My first 2 are 22 months apart and the next 2 are just shy of 3 years apart. We did many things to help the transition:
1) Start before the baby is born with transitioning your son to the "big boy" role - let him climb up into his carseat or chair himself, go get things mommy needs, etc. Make getting bigger something special for him so it's not something he's forced into because there's a new baby.
2) I know people feel differently on this, but I always let my older children come and visit in the hospital. I made sure that the baby was in the bassinet when the older one(s) came in so my arms were open to hug them, and I also always had pictures of my older ones with me in the hospital and even in the bassinet.
3)I was in the hospital for 3-4 days with each (c-sections), and I made sure to call the older ones each night before bed (sometimes other times as well), and daddy was home for tuck in to keep things as normal as possible.
4) I also left a small gift for each from me for each day I was in the hospital. They were inexpensive things, but I also tried to include some craft or activity they could do to pass the time with their grandparents.
5) When I came home, I made an effort to include the older one(s) with the baby, but didn't force it. When my second was born, my oldest didn't even want to get into family pics with us, and I didn't force her to do it. I let her come around in her own time (happened pretty quickly).
6) I tried to set apart some special big girl time every day, during one of the baby's naps. It doesn't have to be much - even 10 minutes reading or doing a simple craft - as long as it's just for her.
7) I made a point of sometimes telling the baby "You have to wait while I help your sister" - even if the baby doesn't particularly need you right then, it will be meaningful to your son to hear he comes first sometimes.
8) Before sitting down to feed the baby, I always made sure to get my older one(s) a drink and snack as well. It helps occupy them and know their needs are important too.
9) While we couldn't always manage the exact same bedtime routine as before the baby came, my husband and I would alternate doing the big kid bedtime so we could keep it as consistent as possible. On the rare occasions that the baby cooperated, we would both do it.
I'm sure there are lots of other things we did. Since you're already thinking about it, I'm sure you'll do just fine and your son will do great. Just give him time. That age gap, though hard at the beginning, is actually great as they'll quickly become best buddies. Good luck and hope some of that helps!