It may seem boring, but it's a wise investment of time to pretreat your fabrics. I try to do this right after my purchase so my lovely fabric is ready when I get a chance to start my project. If you do it right away, you can also jot a note about the fabric info and attach it to the fabric before you put it in your sewing stash. I always carry small sticky notes in my purse so that when I shop I can jot down the care instructions and fiber content from the bolt before I leave the store. I've not always been that thoughtful, but I've learned through the years that I often times pull something out of my stash and can't remember anything about it that is critical to it's care. I also snip off a corner of the fabric to let me know I've already pretreated it (since I store this stuff for years -- see previous post ;)
Pretreating means to wash or clean the fabric as you will when you finish your garment or project. This is important for many reasons. Most importantly is to allow the fabric to shrink before you do any cutting. Shrink-resistance is never a guarantee, and it's better safe than sorry. Dry-clean-only fabrics should also be professionally steamed or at least, steam-pressed at home. By eliminating any residual shrinkage, you will have greater success with your finished garment.
Another reason is to remove the finishes that are applied to prevent soiling and wrinkling by most fabric mills. These resins can be irritating to some and often lead to skipped stitches when sewing. What an aggrevation! When you wash or steam your fabric, you will also learn whether that pesky center crease will disappear or not. If it doesn't, then you can avoid it when you lay out your pattern pieces.
Just launder your washables using the delicate cycle. It's not necessary to use a full cycle. I use my "quick" cycle with a small amount of detergent. If the fabric is especially "ravely", you can zigzag the edges before tossing it into the machine. Dry the fabric the same way you will dry the finished project. For dry-clean-only fabrics, at least steam them before you cut out your project.
Below is a guideline to the meanings of the numbers in the triangular care symbols that you can find at the ends of bolts. I've got this taped to the inside of my laundry room cabinet for ready reference.
1 Machine wash warm
2 Machine wash warm, line dry
3 Machine wash warm, tumble dry, remove promptly
4 Machine wash warm, delicate cycle, tumble dry low, use cool iron
5 Machine wash warm, do not dry clean
6 Hand wash separately, use cool iron
7 Dry clean only
8 Dry clean pile fabric method only
9 Wipe with damp cloth only
10 Machine wash warm, tumble dry, or line dry