I do many counted cross stitch kits and they're pretty big so I always grid my fabric before starting. It helps me line up the stitches and not lose count. If I make a mistake, I can catch it quickly and will have less to frog. I use thin fishing line to grid in squares of 10x10. When you're completely done, you can pull the line from one end and it will come right out without snagging your stitches.
It's really not hard at all. they do recommend that you start from the middle, but I prefer to start from the top corner. The grid allows me to do that with accuracy. Just count the squares from the middle and you're set.
I also make a copy of the pattern so I can use a pencil to shade out areas I've done. I also like to start with a darker color that stands out on my pattern. Do all of that color on that page, and then move onto the next darkest. Making sure to never cross the floss behind the work for more than 3 stitches.
In this picture you can see if you look closely how I make my grid http://photos-371.ll.facebook.com/photos-ll-sf2p/v140/146/68/877985371/n877985371_1514141_3941.jpg
This is another one where you can see the grid in the other direction http://photos-e.ak.facebook.com/photos-ak-sf2p/v241/146/68/877985371/n877985371_2830260_3486.jpg
If the finished product is wider than tall, I grid by horizontally.
If the finished product is taller than wide, I grid vertically. That way the ends of the fishing line are rolled into the frame and not dangling and in my way.