Everyone has a different opinion on which alts are best but ultimately you will have to decide yourself. A good strategy is to start with the main alts which are more stable before looking into the smaller and newer ones which bear a lot more risk.
It's so important to ultimately make your own decisions as then you are responsible for them and you can't blame others if things don't work out. It also then encourages you to really look in to things yourself. I would say starting out check out the ANN threads as well as looking up some of the responses people have listed here. Make sure you take your time to read about the projects and understand them and where they fit in to the crypto space.