How refreshing it is to see most ppl in here give the only honest advice one can give; do your own research.
Read the ANN thread of the coin. All of it! Many coins also have a slack. Join. Also see what they say about the coin in this section or the ANN of competing coins.

Here's a few rules of thumb that can save you a lot of Money.

Never be in a rush to invest. There is plenty of opportunities
Dont go with the hype. By the time it reaches you it's to late to get a good entry if you are new. And often the hype is just that. Hype.
Dont invest in ICO's. You need experience to find the good ones
Stay away from short term trading until you know what you do. You can easily lose 50% of your money in just one day
Stay away from coins with anon dev unless it's an old coin and the dev has a proven track record
Dont bother with coins that are not listed on Poloniex or Bittrex. If they are not listed there then there is mostly a reason for it
Go for coins that have really unique features. Not just minor adjustments to the coin they where cloned from.
Never panic sell unless there are fundamental reasons like dev quiting or other things that seriously damage the project.

You can make a nice profit once in a while by breaking these rules, but you will lose 10x as often until you know what you are doing