Your Curve (regardless the model) is going to have the lowest available memory of any BlackBerry, being an entry-level device.
Keep the apps to a minimum; file or delete everything you can from your Messages application; delete browsing history when possible; reboot the device daily if you have to; make sure the OS is current. These are a few of the things I do to keep my 9330 running somewhat smoothly.
"The price of liberty is eternal vigilance." -Thomas Jefferson
Every blackberry models are good and it is we who made them hang ,So as tsac said please try to remember if you had installed any app and also take control over apps don't install to much apps,there are some good suggestion given above try to follow them.
And yes if any updates are available update your device.