First, always pack the morning of your trip. Never pack the night before. This seems illogical to many people - they don't want to put it off until the last minute. However, this is actually the safest way to avoid forgetting important things. If you pack the night before, you have to leave a number of your important travel items unpacked - alarm clocks, personal items, toiletries - you're going to use all those things in the morning, and you might just leave them at home if you wait. If you must pack the night before, consider alternatives. Make a list of everything you will need that will be left out - then check them off before you leave. Or, you can simply buy a "travel pack" that will duplicate everything you might need.

Second, spend a few hours thinking about what you will be doing. Lists are your friend - they'll make sure that you have everything you need. If you're a frequent traveler, you only have to do it once - many people have found themselves rushing to the department store to buy a tie or shoes that they forgot to bring on an important business trip. Don't be that guy.
About the Author

Teve Torbes is the developer of a great flea control site, who has taken the time to know lots of things about flea medicine. Torbes gets rave reviews for his wonderful inflatable air mattress site.