What can I do to stop forgetting things I should do?
A lot of things come to my mind during the day, about things I should
buy or calls I shoud make, etc. It could happen while driving,
shopping, or even talking to someone else. I usually let them go
hoping that they would come back to my mind at the right time but I've
been proven wrong.
What i'm looking for is a way to record what ever comes to my mind
about things I should do or things I should buy or even things I
should look up in the internet. This could be by using a device or
maybe just a technique to remember effectively or anything else.
If there is a device for this purpose, I want it to be quite small and
very easy to carry(I already have a PDA, but I can't take everywhere
with me).

Have you considered carrying a small digital voice recorder with you?
You could dictate things as they occurred to you, and play back your
verbal messages later, at a convenient time.

Good idea, Pink -- à la "Night Shift"???
http://us.imdb.com/Quotes?0084412

willowdale...

Abe Lincoln supposedly put notes inside his top hat.
Since I'm a smoker more than a hat wearer, I just
carry a pen at all times, and jot notes on the pack
of cigarettes. It would be just as simple to use
a folded piece of 8 1/2 X 11 paper in your shirt 
pocket, and jot keywords on it as things come to 
mind. I've used this quite effectively in a very
complex job situation as a Case Manager, when the
cigarette pack wouldn't provide enough room.
Every time you make a new entry, you can browse 
the earlier ones. This always served me well.

There's always... oops, I forgot.

My cellphone has a NOTES feature, I just push a button and talk and
can retreive my "Notes" anytime I choose. Your cell phone may have
that feature as well, have you checked?

Mine is a Motorola P280...

~~Cynthia

Along the same lines as Cynthia's cell phone idea.  If you have a cell
phone, you can call home and leave yourself a message on your
answering machine.

I personally carry a calendar around with me and write things down in
it.