Because the PSP itself slightly interferes with the reception of the PSP-290 GPS receiver, you can increase reception by moving the GPS receiver away from the PSP by connecting an extension cable. This cable can be bought fromPCMobile. Several users have reported a faster fix and more satellites in view using this cable.
Format your memory stick as FAT32 (not FAT), you'll be able to put much more map data on it. You do need to restart your PSP afterwards.
Of course be sure to make a backup of the contents of your memory stick beforehand.
Formatting as FAT32 should also work on a Mac (choose "PC DOS" as format).
You can use BlackVenom'sPSP Game Structure Utility to sort the applications in XMB.