I am a huge metroid fan, which is why I started playing Samus. If you play a lot of metroid, you will know a lot about Samus.
1st, she is a beast. She can take a lot of pummeling and come back to the fight. If you know in any metroid game, you can bounce off of the bombs. So, when coming back to the stage, drop a bomb, then, as you fall beneath it, drop another one as soon as possible. If done correctly, you should bounce off the first and dramatically ease re-entry to the battlefield. Keep doing this over and over until you get back to the plane of fighting. If that's not enough to get you back, don't forget her grapple beam. Just like in metroid, you can use the grapple beam to latch on to walls so that you can recover. The big secret is that you can air dodge and then grapple! This stops you momentum and allows you to easily grab the edge. If you air dodge up, you can get a little more out of it and can hopefully recover better!
2nd, missiles. Use lots and lots of missiles. Pretend you are in super metroid, except now you have unlimited missiles... freaking amazing right? When in doubt, spam missiles. One of the easiest tricks with Sammy is to jump in the air and land just as you are firing a missile. The missile will come out, and all the lag from the attack will never occur. This can lead to dashing with the missile, charge shot as the missile goes, F smash with it, or simply shoot another! If someone says you are spamming, shut them up with more missiles.
3rd, regular tech stuff. If you don't know the normal stuff, go check it out somewhere. But basically, Samus has a solid WD. It has fair distance and you will find it to be very useful. She has one of, if not best, crouch cancels in the game. More often than not, you are going to be wondering what you can't CC than what you can. Basic combos with this are CC to d tilt, CC to screw attack, or CC to f smash. Short hopping won't be a concern for you until you get into the more complex things, so you may not have to worry about that with her right now, same for L-Canceling.
4th, the tilts. Samus's Up, Forward, and Down tilts are simply amazing. Edgegaurding with up tilts is usually good, save for a few situations. Forward tilts can be directed above, mid, and below. Directing these properly will make any sad panda... not sad. D tilt combos into a lot of things. Neutral air, back air, D air, F smash, F tilt, Up tilt, etc.. That's why CC to D tilt is sooooo good.Sometimes, it is best to f tilt instead of f smash. If you smash and miss, you could get grabbed or worse. F tilt is faster, bigger, while yet weaker. Don't be afraid to use it. Her dash attack, while one of the few that can actually kill at a reasonable percent, DON'T SPAM IT!!!!!!!!!!!!!!!!! It has its uses, but windmill of fury should be kept a secret
Lastly, bomb ****. Bombs are your big counter. Drop a bomb and you can, wave bomb, bomb hop MC, stop someone's WD, stop approaches, and **** shields. If you master bombs, it will give you a huge advantage in the long run. Maneuvering from bomb to bomb adds not only to your mind games, but allows you to go from ground moves to aerials instantly. You can cancel some moves with them, add damage to a grab, or, my favorite, knock them into a bomb and then hit them again while they are stunned (X bomb combo).
If you want to get serius with Samus, learn the basics first. Then learn her specific "Samus only" type moves like Missile Canceling. Then you can move on to advanced things like the SWD, 3rd Jump, and effectively using the extender. Good luck!