For people who have experience teaming with a Fox as Sheik, what is it that I should be looking for/doing? I have experience teaming with a Peach and a Falcon, but I teamed with a Fox player recently, and I just felt kinda lost. Any advice is welcome!
Playing with a fox is very different than playing with falcon or peach. Falcon and (especially) Peach are more geared towards a support role. This means that as a sheik main you are forced to be more aggressive because you have better combo starters than your teammates. Fox, however, has very good offensive tools. This allows sheik to take a full support role. As a sheik teaming with a fox your job is to help your teammate by breaking up opponent's combos, continuing your teammate's combos and making opportunistic edge-guards. Stock tanking is also super important with a fox teammate. This is because fox can die super quickly off of one mistake.
If you want to see a great example of how to team with a fox watch the sets of Mafia and Leffen teaming at summit 3. This is a Peach Fox team but it is still worth watching because mafia does a great job playing the support role.
As far as things to look for, Fox is very good at getting the opponent off stage. Be ready for this because edge-gaurding will fall mostly on you. While fox has an amazing edge-gaurding game, going off stage is super dangerous for fax if an opponent is off stage. Whenever possible you should be the one going off stage to edge-gaurd. This is because edge-gaurds against sheik tend to be very long so your teammate can save you. Edge-gaurds against fox on the other hand can be over in seconds.
I hope that this was helpful for you.