5 month old sleep training?

Wondering if any moms have good tips or things that worked for you when sleep training baby, he's 5 months old and WILL NOT nap unless someone is holding him, when I lay him down in his crib he sleeps for 2 minutes and wakes up crying.. I've been co sleeping at night also and want to transition him to his crib, he'll sleep in it at night for about 2 hours then cry and not go back to sleep unless I pick him up.. wondering if I should try letting him cry it out?