I have a 5 week old DS (my first and only) and during the day I can quite easily put him down to sleep once he's eaten his fill. At night it's a different matter - it can take 1-2hours if holding him /trying and failing to put him down, before he'll stay asleep for more than 15 mins. Tonight is a prime example - I fed from 9-10.30 and he's just been put in his crib for the third time at 1am (I'm just waiting to see if he wakes again).
I've tried a variety of things (admittedly only once or twice for each):
Ewan the sheep
Muslin which smells of me as a sheet
Hot water bottle to warm his mattress
Rocking his crib
Swaddling / grosnug sleeping bag
Any tips?