What is the best way to move around between games. ie how do many of you pick previous games? Going back using prev button? or via selection (which I am unsure of how to do that)

Click "Play", then "View Game Archive" to get a list of all games on a calendar.
If you want to redo games you have already completed, click "My Stats" on the top right.

@ash, there are several ways to move through the games. If you want to play a game that you have not completed yet you can select the Easy, Medium or Hard links at the top of any page. It will congratulate you when you have completed all of the games in the selected skill level.

As @xavor pointed out, you can can browse through games using a visual calendar by clicking the 'View Game Archive' button on the main page. If you want to view games that you have rated you can click 'View My Ratings' on the same page (this lets you visually see which games you have not completed, which games you have completed and what you rated each game).

Alternatively, if you have played most of the games and you want to increase your score, you can click 'My Profile' at the top right of the page. Scroll down and click 'View all stats'. Go towards the end of the list and click the game number in the second to right column.

I tend to go to my ratings & try to improve the lower ones.