Research! You can never do too much of it. Ask as many questions as you can and when you are done, ask some more. Join discussion channels (like telegram) specific to the alt you are thinking about investing in and ask even more questions.
Those are good recommendations and telegrams or slack is on way how to get latest developments of every projected altcoins ico's to invest. By the time you are holding your altcoins into long term goals, I think you should have more months to take just to hold the coins that you have. Selling your assets is the last portions as your income will increase by the exact time sell value of your assets also rises higher, and you easily decide to sell you holdings.