just to build on what richardtallent said...
3/4 inch solid oak floors can handle 3 refinishes we were told. beyond 3 and the wood is to thin.
this is very very dirty work. the dust will get everywhere. when we did out first floor, we had just remodeled the kitchen. make sure you tape off any rooms you want to keep clean with heavy plastic and painters tape.
tape up any heat registers and returns. change your furnace filter (if you have a furnace) before and after. if your doing this while you need the furnace (summer or winter) check the filter during the process.
we did 3 passes on ours (they had never been refinished and were original to the house) from course to medium and finally fine. ours was a complete gut, so we didnt have to get around floor molding, we replaced it with new stuff afterwords. orbital sanders (the one u stand to use) are powerful. if you use belt sanders you can go with the grain producing a better product.
watch for popped nail heads. sink them when you can. they eat sand paper.
fill in any gaps with wood filer to match the floor. stain will stick to it and the poly will protect it. major flaws in the floor should be fixed. even though my house is over 80 years old, lumber liquidators still sold the oak wood.
keep the work area clean and vacumed. we used an every day shopvac and it had to be cleaned constantly.
we used belt sanders and did it by hand on our hands and knees. alot more work but allows for much finer control. if your not paying attention, you'll gouge the floor. feel the floor with your hands as you work. there will be so much dust on it, you wont see it with your eyes. good wrap around eye protection too. you'll cry saw dust at the end of the day.
2 coats of stain, waiting a day in between and 2 coats of poly (minwax) waiting a full 7 days in between. the fumes are amazing. get some fans to help circulate the air. if you insist on sleeping in the house when the poly dries, do not step on the floors for atleast 24 hours after each coat, and becareful for the next 24 hours. our front door is feet from the stairs to the 2nd floor, so we setup a plank to get out of the house for work.
tack cloths are your friend; use them between each pass of staining and poly.
make sure the place is spotless while staining and poly; we made 2 passes each time we stained or poly (there were 4 of us working on the floors at the same time)
its ALOT of hard work. get a good mask, not the crap paper ones. keep the windows open and blast the music.
i'd go out for a smoke and you could just see saw dust pouring out of the windows. it will get everywhere. clean the walls, the ceiling. then clean them again.
every aspect of this is finish work, even the sanding. each step will determine how good the next comes out. take your time.