Hey man, I just went through all the stuff your going through now, be werry on what advice you take from the forums. its 50/50 on fact to opinion! If you have a awsome LFS, their advice will be very consitance, so its pretty trustworthy.
so on that note, if you know for sure your tank is cycled, then go for a larger water change. l'd say like 50% if you haven't done any small ones yet. after that you can start a routne! I do 10% once a week. I waited about a week after my first big water change before I got my CUC. but the LFS said 1 snail per gallon, and a couple hermits! umm I dont remember what kind of snails I have, but in the small tank I went for the mexican red tips! they are less aggresive on eatting snails than the blue leg from what research I did. as for Shrimp, I went for the basic cleaner shrimp, I think they call it the Scarlet Skunk cleaner shrimp, its the one with the red strip down its back, and yellow on its belly! they seem to be very hardy from what I read/hear, I'd even go for two of them in a 20g! I was reading that they are much more playful in pairs or 3's. so I cant really give much more advice, I haven't got past the CUC, fish are coming in about 2 weeks for me! good luck!