After having a tooth pulled, how long should you keep gauze in for? When can you have yogurt and fluids?

Typically about 30 . Minutes if there is no bleeding. If the bleeding persists, then place a wad of new gauze and repeat as needed. I'm surprised that the doctor did not give you a post-op instruction sheet outlining the do's and dont's. Once the numbness has worn off you can resume with limited foods and liquids. I would call the doctors office for more instructions. Hope this helps.
Short time. I would recommend 20-30 minutes which will allow the clot to form. Pressure from biting on the gauze is the key.
Depends on factors. Depending on the location of the tooth, the condition the tooth was in, was it a surgical removal, are there any sutures, was it baby tooth? Did you take Aspirin or Motrin for any signif time prior the extraction, are you on a blood thinner, are your currently cycling...For a simple orthodontic extraction- 20 min should be good enough- we are hoping for a primary clot. A cool teabag for addn oozing.