Pretend you are playing tic-tac-toe and draw the grid out on a piece of paper. Now, you would bring your needle up in the lower left corner and put it down through the upper right corner -- crossing over the square in the middle. Then to cross it, you'd come up in the lower right and down in the upper left, once again, crossing over the square in the middle. That is now once stitch done over two threads. Another way to help you count this while you are stitching is to bring up your needle in one hole, and then count two threads over and two threads up, and that is where the needle goes down.
Depending on what you want to do.. a sampler, a design from a photograph, a design of your own, etc. there are a variety of different methods. This isn't a very easy question to answer. :-)
There are several computer programs out there to help - PC Stitch, Stitch-A-Photo, Pattern Maker Software, Pattern Maker Cross Stitch Clipart, and I'm sure there are more. These software programs will help and provide you small images that can be used in your designs.
If you are trying to do a sampler of sorts you could just start with a book of drawn thread and cross stitch stitches and design your own on a piece of graph paper.
I would think the 'simplified' version is to find a software program that provides you with some of the functionality you are looking for.