Alright i'm gonna drop my three white guy tips for freestyling, because I guess it comes really easy to me. I've been freestyling on my commutes for years, and I can't do it every time but I'll freestyle completely off the noggin, non-stop for 10 minutes and it'll actually be good if i'm feeling it. This is one of my few skills, so I'm gonna put a lot of effort into this comment. Seriously, this shit will be helpful.
Practice more.
Not just freestyling, but writing as well. I know a lot of guys who don't write because "poems are gay". Well their bars suck, and that's why. Freestyling isn't just picking words out of the dictionary and rhyming with them, it's memorizing patterns and rhymes to create your own mental dictionary.
Think less.
I don't really know how to explain it but i've always said I freestyle on instinct. Maybe it's just me, but I can't think and rap at the same time for more than a couple lines. It's too hard for me to multitask searching for rhymes as well as content, but I still want my freestyles to have both good rhymes and good content. So, I practiced freestyling without thinking. To do this, you have to freestyle, without thinking. Yeah, I know that doesn't make sense, just bear with me.
Cusswords make great filler.
When you've got a feel for the beat, you should be able to tell if the sentence you're saying will fit or not. If it's too long, you can change up the rhyme scheme, cut out some words, or get creative with it. If it's too short, a cussword can't hurt. One syllable? Fuck fits almost anything. Two? Fucking. Other favorites include shit, bitch, and dick. I don't like cunt, because I always try to rhyme it with month, and "munt" sounds fucking stupid.
So you're reading this and you're thinking i'm saying the same old shit, right? Well this explanation might explain things a little better for you.
Remember that mental dictionary I mentioned? Well, basically I have a dictionary of sounds. For every sound or syllable, I know a fair few phrases, words, sounds, and syllables that rhyme with it. Obviously you aren't in a position where you can just start freestyling without thinking. I'm not telling you to go try to memorize a bunch of stuff, but just make that your goal when you are freestyling.
You want to get to the point where you have so many syllables, words, phrases, lines, and even bars in your dictionary, and you want them to be connected to each other so you don't need to think about which direction you're trying to take a rap in. By this I mean you want to understand the emotion and the meaning behind everything you say, and the way that everything in your dictionary interacts with each other when used together (because the meaning of a word depends on the context it is said in) without having to think about it If you understand these things without having to think about it, then you will be able to finish a bar just by the way the first line feels to you. When i'm really in the zone, my mind is completely clear and i'm just telling a brand new, unique, rhyming story, completely from instinct.
"Yeah yeah Mr. dictionary, i'm not putting in all that work" Well... Yes, you are. Don't go off reading dictionaries and studying rhyme theory, but when you are freestyling, you are already putting in work. Why would you waste your time freestyling any other way? Everything is skill based. You have the ability to do it, but the ability to do it well comes from experience. You wanna get good? You gotta practice. I'm telling you how to freestyle like a god. How to freestyle the same way logic writes. If you want to do that, then do this. So how do you build this mental dictionary?
Try to do the things i'm about to list about, but first and foremost you need to practice. Like I said, i've been doing this on my commutes for years. At my current job, my commute is 30 minutes, my last one was an hour. Yes, practice more. Here's a list.
understand the different definitions of a word, the ways a word can be used, and which other words can be used with it without having to think about it. Since the definition of a word depends entirely on the words surrounding it, you need to be able to "autopilot" a sentence that fits with the word you want to rhyme with. Basically, any thinking you're doing should be focused on the rhyme, and you want to be able to fill in the rest of the line off of instinct.
Be original, be creative, don't be repetitive. A lot of what i'm saying sounds like "memorize lines and put them together when you freestyle" but I really don't mean that. After a long time of doing what you will literally have done is memorized all the many different ways that you can convey whatever message you intend to convey, and you will be able to combine them endlessly without thinking. Basically, you're memorizing every line that you could ever possibly use.
TL;DR There are two ways to freestyle like a god. The first way is to memorize every line that could ever possible be used. The second way is to do everything i've just written. Here's a timeline for how your freestyling will progress.
A lot of guys start out freestyling like this:
I just got home
I've got some pizza
It's really good
It's got some cheese-a
As you practice more, you'll have more rhymes stored in their mental dictionary/rhymebook/content creator that they will be able to string something like this together in a freestyle
This ain't a chessboard
But you're still a pawn
You've been gettin ignored
Since the day you were born
On paper, it's C grade. It's got an ABAB rhyme structure, but the rhymes aren't perfect, they're just near rhymes. There were no other rhyming words apart of the end rhymes, but there was a decent pun and a decent insult. Those are apparently two of the many things that make up good content. I would tell you more aspects of great content but fuck you, make your own style.
Around this point I would suggest switching to my method. After a good bit of practice you'll be able to spit lines like this without thinking about it.
No sugar, I won't treat you sweet
I'm a butcher, I just got the meat
You a booger, and bitch I pick you
You gon' see what a real hard nigga can do
Yeah, maybe the booger line was lame but the fact still stands that it is high quality rhyming. Rhyme structure ABDBAC-C, would only be improved by adding another A rhyme in the fourth line, but I couldn't fit it in. The A rhyme (sugar, booger) is a perfect two syllable rhyme, D is a near-rhyme with A, and while the B and C rhymes were simple 1 syllable words, each line had an end rhyme and there were three additional rhymes throughout the bar. If you have enough natural talent to fit that into a beat, it actually sounds pretty dope. The booger line was lame though.
If you keep on practicing for a really long time you'll start spitting stuff like these. Here's a couple things I freestyled couple weeks back, I wrote them down because i'm going to make an album one day. You'll see that none of them would be truly amazing by themselves, because they need to be edited and finetuned to fit the context of the song.
I keep my cash liquid and my gold solid
Au better get it quick cus i'm a gold-holic
I got the midas flow, it's fuckin symbolic
And it's all I fuckin do, guess i'm a workaholic
I never lost on purpose,
Never won on accident.
You can hate me if you want,
But talking shit don't pay the rent
I don't wanna say i'm the best, that should be obvious.
rest of y'all gon fail all the tests, you just some hobbyists.
step up and i'll send you to death, sit in the audience.
don't get up start wasting ya breath, just stay anonymous.
They look difficult and complex, but honestly the only thought I put into it was best->test, death->breath, obvious->hobbyists->audience->anonymous. I created the first line, but everything afterwards was just a semi-subconscious reaction to it.
I spend a lot of time thinking, and those are all my thoughts on the subject. Here's a pre-written verse I made out of freestyled bars. Obviously the way I fit them into the beat is really important but I haven't recorded it yet so here you go.
I got a castle, i'm a motherfucking king.
You're a peasant in the street, I don't owe you a thing.
If you're a prodigy, maybe take you under my wing,
You're probably not, cus every little birdie can sing.
And if you think I can freestyle,
You gon' be disappointed.
Cus when I try to rhyme my -
mind is always gettin disjointed.
But if you give it time, let it
sit and run through your mind,
let it unwind, maybe then you
find, my flow is on point.
Got a lot of layers, gotta pay
attention to get what i'm sayin.
Understand, you don't get this
good from hoping and praying.
I'm the man, last few years
I been workin' n' trainin'.
Got a plan, i'm hittin hard,
now i'm bringin' the pain in.