You can do what is called a hard read. A hard read is basically a prediction as to what your opponent might do. Some hard reads are quite easy to perform as others aren't. All you do is try to punish them. You can go with a down smash for many of the characters since it can harm the opponent from the front or back. It's a pretty simple way to punish it if they roll in front/behind you. Also, consider the moveset of each of the characters. Certain specials can read moves like ganondorf's side b or his down b. They only work if the opponent rolls back. Don't spam it too often because it deals a lot less damage than a down smash. It can also be very easy to read if you make a habit of dodging and then going for a down smash. If you're talking about the characters like robin or duck hunt, that's gonna be an issue if you have to physically attack your opponent. It can be very annoying. Here's a tip about the up smash. I find it easier to use an up smash when using the c stick. Nothing else seems to work out nicely. But that doesn't mean you can't use it in battle. When you dash, there are very limited options for what you can do. You can grab, jump, turn back and do a side tilt, dash attack, use a special, an up smash, or shield. (you can only do this once you stop dashing.) Using the up smash while dashing can be quite useful but it can make you very vulnerable. These are just a few tips.
