When cutting out your patterns on fabric there are times when you need to mark things onto the fabric, for example when you have a drill hole in the pattern. There are several ways you can do this so you have a mark that isn't permanent.
Chalk - marking in chalk is easy and can be either brushed off or washed off with a damp cloth. Chalk can be bought in different colours so it will show up on a range of fabrics and can be either a piece of chalk or In pencil form.
Thread - put a little stitch into your fabric to mark it which can then be removed once you've finished. This is called a tailors tack. This is a great way of marking your fabric with no danger of leaving a permanent mark. The downside is it's more labour intensive and stitches can fall out if you're not careful.
Pens - there are many different pens available from marking fabric, from washout pens to disappearing ink, they work with varying success so are worth testing out on a scrap of fabric before you use them on your final garments.
Frixion pen - these are the greatest invention ever when it comes to marking fabric. These pens are made by pilot and are supposed to be used as erasable pens where heat created from the friction of rubbing out erases the ink from paper, but when used on fabric you can use the heat from an iron to erase the ink. The only down side to this is great invention is the pen marks can return with extreme cold so don't go wild when marking!