I did this, it is very hard but there are things you can do to help put your mind at rest.
If you do this choose the adoptive parents wisely. Although my child's adoption was closed, could pick certain characteristics. That his adoptive family be of the same race seemed important so that there weren't immediate questions about his status within the family when he is out and about. Oddly, I later gave birth to and raised a child who didn't look anything like my husband nor I and people are pretty rude with the questions. The questions were mostly directed to whether my husband was the baby daddy. My stock answer eventually was, "If (husband) isn't the father, then I'm not the mother and I gave birth to him." That was enough to end that topic of conversation.
The next priority was the education of the adoptive parents. It may sound snobbish but since you can't ask for an IQ test the next best way to hopefully land smart parents is to pick well educated people. It's certainly no guarantee, but if you pick STEM majors or a top tier college graduates you probably will end up with smart adoptive parents. That matters because for a good while they will be making all choices for this child and you want a strong foundation. You'll meet them so that should help too.
That leads to another touchy subject although I don't feel the slights bit guilty about it, money. If I had been able to afford it I would have kept the child, so I reasoned that he should have the things I couldn't provide him. I'm not talking super rich, just people who will never worry, be able to take a vacation now and then and afford college for the baby. Depending on location those things would require a household income of around $150,000 or more now.
Something I wish I'd asked for is a family of like mind, by that I mean politics. The world is different now, but if a family thought that Trump was a godlike savior they would not be considered by me because they believe things that are false, I would have wanted people firmly planted in reality.
That leads to religion, or lack thereof, how important that is to you or whether you'd prefer they are atheist.
If you don't believe in god research agencies which do not have a religious affiliation or if those are places you don't feel good about, pick religious agencies where the faith is less intrusive. Liberal Jews and rank and file Episcopalians generally are either atheist or aren't nuts in their religious fervor.
Private adoption isn't a great idea because regulation is poor (in general) so babies go to the highest bidder, you want parents who are fully and carefully vetted.
Think about things that will help him match his new family, do you like the outdoors? Lean toward people with similar interests to you whatever they are. But this shouldn't be a show stopper because people give birth to and raise kids who they just don't understand and visa versa.
It was very important to me that he be with his new family as quickly as legally allowed. Although I hated everything about it for me it mattered that they have the newborn period together.
Chose open adoption and think about whether you can let his new family raise him.
Best luck