What is the difference between using steam versus sizing versus nothing at all when you iron your fabric before you use it? Since prewashing will leave wrinkles in the material you will have to do something to get rid of said wrinkles and I am just curious as to what the best method is.

I press all of my fabrics after I wash them to go into the stash. I try to get them from the drier before fully dry, usually I forget. I always press everything with a dry iron, I seem to be a little over zeazlous and strech things when I use steam. I always keep a spray bottle with distilled water on the ironing board. For some reason, I do not strech the wet fabrics like I do when I use steam.

Depends on the fabrics - some of them come out of the dryer relatively smooth and then I just "hand press" them when I fold them and add them to the stash.

I'll have to iron it again before cutting, so I see no need to press at that stage.

I will iron it before stowing it if it's really rumpled just to make it take up less space.

I use a very light steam when I iron the fabric before cutting.

I very rarely use starch or sizing. When I try using that, the fabric seems to stretch - I'm not sure if I'm overly zealous with my ironing/pressing or what -

The best I have found is like Pam said, don't dry them completely and iron over lightly. wrinkles come out very well that way, if the cotton is the type that tends to wrinkle alot. Some can wash and dry and iron quickly cuz not much wrinkling in the wash or drying process. I don't really use starch either .. I will some if the pieces are going to real small, otherwise I don't .
Sharon

Finishing the raw edges (serge or overcast) before washing minimizes tangling and fraying.

It also helps to minimize wrinkling if the dryer is less than 1/3 full when drying fabric.

It one is washing and drying long narrow strips of fabric (regular 1/4 yards and less), it helps to fold it in half - printed sides together - selvage to selvage - and pin the ends together. Minimizes tangling and wrinkling, also.

When the fabric is washed and dried, I spray it with starch and let it dry. That way, when I iron it with steam it does not distort.
I used to iron/steam it every which way, and it would distort. Now I lay it on the board, laying the fabric's selvedeages parallel to the sides of the board and iron straight up and down and side to side. If I move the iron diagonally or in a circular motion, it will stretch/distort the fabric.

I also usually iron it from the back so I can see the grain lines.

Like Amma said, I go with the grain lines. And I usually start from the center and work out towards the selvages. I have a Big Board so that works well - except when the cat wants to "help"

So far, I've avoided ironing his toes or tail.

I use water spray when ironing yardage after washing. If I am going to be cutting small pieces then I use starch to help avoid stretching of bias edges on small pieces. Once I cut fabric, I never use steam on them, because of the stretch factor...just hot dry iron.

I press the fabric after it's been in the the drier, but I don't use sizing or spray starch until I'm ready to cut the fabric. Bugs love the taste of starch and fabric finish. But I do use them when I'm ready to cut because it gives the fabric the stiffness needed which was lost when the fabric was washed.

I use nothing. Just works well for me.