how can I make a good thumbnail picture for twitter?

[Jesus]

I've seen people with good quality photos as their default and mine always comes out all blurry :/ is there anything I can use to make a good looking thumbnail instead of letting twitter shrink my photos automaticaly?

[Goinglogo]

XnView is a utility for viewing and converting graphic files.

You can find a link to download it here:
http://www.goinglogo.co.uk/index.html

Once you have downloaded it, open up the file, then from the menu select Image|resize.

Once you have it at the right size, do File|Save as

Its all straightforward from there.