*Is a master at using Fox and Link, especially*
If you're just starting with Fox, get used to using speed over power. Charging in directly full force isn't going to help you at all. What you need to do is rush in, land 4 or 5 blows, or two Fox illusions, if you can. Use short, small bursts of moves in succession, if you can. This is a great way to help you get started.
With Link however...
Link can take a few more blows than Fox can, due to his defense, and weight being a little higher. Spin attack, and Up-A are some of your best friends while using Link. Try to keep your opponents up in the air as long as you can. If you are knock high into the air, Down-A is the best move. Make sure you hit your target. Remember, the higher you use it, the more attack power. Grabs help a LOT when it comes to finishers. Jump and use down-b, spin attack, or grab, and your opponent is bound to go flying. Make use of Link's defense though, seeing as he can take some rather tough hits. Bombs are good for stallers, if there is an item you need, or if you want to make a quick getaway. These tips are useful for people just starting out, and if you get better, I can explain in better detail.
Also, if this post is tl;dr, then okay, that's cool too. I'm one of the upper-class players, as long as I can have Link, Fox, or Marth.