You didn't mention how old your son is, so if he's under 1 then you'll have to use formula and if he's less than about 6 months your supply may suffer as you remove feedings and might not be able to continue breastfeeding at all.
I can tell you what happened with mine. I decided I couldn't handle the pumping anymore when he was about a week from his first birthday, so I wanted to wean him during the day. I took out one feeding during the day per week and substituted milk and a snack. He resisted at first (according to the sitter), but within a few days he was fine. I tended to give him a snack I knew he loved, oranges were his favorite at the time. I wasn't in a hurry to wean him completely, but the pumping was too hard at work and I wasn't getting enough to keep up with him. So within a couple of weeks I was done pumping and he was just nursing in the morning and before bed. After a couple of months he just asked to take his bath without nursing (our routine was nurse, bath, books, bed). Probably a month or so after that he didn't want to nurse in the morning and just wanted to go downstairs and get breakfast. So he self-weaned around 16 months. I'm sure not all kids will do that, but if the pumping is the problem for you I'd start with the daytime feedings and then let him lead from there.