this is my method having had dd1 who dropped her nap at 18 months and dd2 now looks like she will drop her nap soon, just gone 1 yr! don't know why i have such crap sleepers but there you go. most valuable thing to me is my evenings so i gear sleeping towards getting a bit of time to myself, whatever it takes.
first thing to do is try and work out how long they have to be awake for before they'll sleep well when you put them down at 6.30 / 7pm. so if they wake at 2, will they go down at 7? if not, try waking them at 1.45, then 1.30 etc.
that is not foolproof though, because if they sleep too deeply at lunch they won't go down in evening either. so you also need to work out how long the lunchtime nap should be.
your dc don't need as much sleep as all the books say. best to accept that they won't be having 3 hour naps and 13 hour sleeps like all your friends' perfect babies. crap, but there you go. we work with what we've got and love them anyway . in a few years this will all have settled down and we won't be able to wake them.
at the moment, i think dd2 needs to nap anywhere between 11.30 and 12.30 and sleeps no later than 1.15 for no longer than 45 minutes. although she was up at 5.45 this morning so might cut that back to 30 mins.
i need to have a method to function. i hate guess work and not knowing what's going to happen esp if i have a night out planned. you end up having no life then. so i err on less sleep during the day to get a bit more peace at night.
broms, i have huge sympathy for you. i don't know if my method will work for you as yours isn't sleeping for very long at a stretch. what are you doing to settle him?