What works for me is, ideally, you ask people out when you become friends. I consider another person my friend if they are:

1) Sharing details about their lives that normally isn't shared. 2) Hanging out with you at their leisure times, rather than just at work/while studying.

By that time, I'll also know what this person thinks of me, how I view them, whether they already have other romantic interests or not, etc.

Also, making it super direct can potentially damage a platonic relationship. Like "hey do you want to go on a date". If they say no, things become awkward. So I try to give them an out, like "hey do you wanna have coffee sometime at X, I wanted to try it out?". And let them decide whether to take it up or not. If they say no, I'll try to diffuse tension by pretending they hate X and cracking jokes about it. And I move on.

But I'm as imperfect as anyone else, so take this with a huge pail of salt. Also every person is different (and relationships are complicated), so tough to give a generalized answer.