Now there is no way that you're going to memorize them all, but what I think is efficient is to figure out something you're doing often, and to look up the hotkeys for that feature.
No, not THAT type of hotkey.
I've blogged in the past about some of these hot keys, but in the process of updating Microsoft Office, they've removed some of the hotkeys that I personally was used to, which makes me sad, but they've also added some, which is nice.
Where do you look those up? Well, if you Google it, you'll get a list, but at this point, you're dealing with a lot of people who have the Office 2003 lists up. You would figure that there's a comprehensive list for each of the programs on Microsoft's site ... but you'd be wrong. As far as I can find, they only have a set of Office 2003 shortcut keys on the site, not the Office 2007 ones.
One site that I've used for this purpose in the past is keyxl.com and they've done an excellent job of laying out shortcuts for the major Office tools at the links below. Definitely worth a look if you're wondering something like "How do I start a slide show from this slide instead of slide one?"**
- Microsoft Word 2007 hotkeys
- Microsoft Excel 2007 hotkeys
- Microsoft Access 2007 hotkeys
- Microsoft PowerPoint 2007 hotkeys
** Answer - hold shift and hit f5