First peice of advice before getting fish, is get tank set up in location you like cuz once its filled it is pretty much stuck there for long haul. I would get it set in place, choose substrate (rock/sand) Live plant, false plant... then put it all together, get filter running on it for a few days then do a fishless cycle. This will allow safe tank setup and let you chose the type fish you want and save them the stress of cycling a tank. It takes more patience this way but it is better in long run IMHO. While setting up tank you can surf the forums for ideas on layouts and doing this will give you idea of what type fish you want i.e. aggressive, community, semi-aggresive. each type has different needs my tank is setup for bottom dwellers i.e. loaches, eels, catfish. I have some schooling fish to complete the look. So once you know what type you want then you can get good estimate on amount of fish. Schools of fish= more fish in tank, but big fish i.e. clown loach and yo yo loach will need more space so less fish.
In my 60 gallon i had 45 fish in at one time now down to 37 all parameters are in green zones with monthly w/c. for pics of my tank look for posts by me and you will get idea of my tank layout and what it is holding.