-Try not to play close to the edge. You get grabbed near the edge, you should be dead no matter what percent you're at.
-If you hit their shield with an aerial, know how to use shield pressure (especially shine grab) effectively to prevent them from shield grabbing you, because Shiek's grab punishes are enormous.
-Don't get grabbed in general. This means space your aerials, shine immediately after your aerials landing lag if applicable, and don't throw out unsafe moves. Oh, and you need your L cancels to be 100%. Sheik feeds on that. Tbis is generic advice that you should keep in mind against any character, but its especially important against Sheik
-If you do get caught and are being tech chased, mix up your tech options. However, know based on the percentage and where you are on the stage which tech option is going to put you in the least bad position (remember that I said you don't want to play too close to the edge).
-Don't be predictable with your double jump. She will needle you out of your double jump and make you want to curl up in a ball and cry.
-Don't let her charge up needles for free. If you are close enough to punish the needle charge with a nair/dair/shine/grab/etc look out for the spotdodge. If you aren't close enough to punish with one of those moves, atleast put on some laser damage.
-waveshine>upsmash.
-waveshine>waveshine>waveshine>upsmash
-seriously man, you have waveshine>upsmash. Win the match lmao
-Sooo often I see people holding the ledge, Sheik up b's, and the person just gets off the ledge. Sheik players think they are tricky. I would say 50% of the time, they will up b to the ledge even if you are holding it. Just hold the ledge. UNLESS she can up b to a platform. Sheiks loooove to up b to platforms. If you are in and edgeguard situation holding the ledge on yoshi's, battlefield, or fountain (but only fountain when the platforms are low) and you think the Sheik is going to up b to a platform, you can ledgehop>waveland (or ledgedash if you prefer) directly onto the platform, and probably get an upsmash because there is so much landing lag on Sheik's up b. On these stages, you can probably just hold the ledge incase Sheik up b's to the ledge, then when you see that she has up b'ed to either the stage or the platform, ledgedash accordingly to punish.
-There are certain matchups where you want to go in and go ham, and push your advantages really far because you aren't afraid of getting grabbed and their punishes typically take set up - like falco. The Sheik match up is not one of these matchups. You ARE afraid of getting grabbed, and if you aren't then you should be. Don't over extend yourself. Know which of Sheik's moves that you can safely punish and how, and don't go in unless you are fairly confident that you can get a hit. You can be content to use your superior dash dance/movement speed to camp her out and rack up laser damage until you find a proper opening. Or atleast this is how i like to play the match up.
-Try to notice her needle pattern (when she likes to charge them and when she likes to throw them) so that you can position yourself to be able to dodge them.
All in all, Sheik is a character that has an incredible punish game on fox, but if fox gets her in the air she has a very hard time coming down. Your projectile should win out in a camping war if used correctly, so don't feel like you need to approach too much. She should never be living to over 120% at the most, because you literally have a one frame move that combos into the second best upsmash in the game. ABUSE WAVESHINE UPSMASH
Last tip, but its probably the most important one: if you want to learn about a specific match up, watch pro matches of that match up, except don't you dare watch them passively. While analysing matches, if you really want to learn from them, pause the video every time someone gets a solid punish. In this case, if Sheik hits Fox, rewind and see what Fox could have done differently not to get hit, try to understand why each person made the decisions they did leading up to the hit, and think about what you would have done in that situation verses what you should have done. If Fox hits Sheik, do the same, except really think about what made the Sheik vulnerable and how you can look for that/exploit it in your own opponents. Likewise, after the initial hit, see if they got any follow ups. Think about why they chose the moves they did in the interests of getting more follow ups and ultimately taking the stock. If they didn't follow up spectacularly, think about what they could have done differently to get more followups. Should they have used the weak hit box of a move? Should they have used a different move entirely? And always be asking yourself why. These players had their match streamed and you went and found it on youtube for one reason: they are GOOD. They, for the most part, no what they are doing and have a reason for every move they use. Really try to understand what they were thinking.
Oh, and if you didn't know, space bar pauses and the arrow keys go forward/backward a couple seconds in youtube. Using these makes it so much easier to rewind every time you see an enounter you want to analyze
