Delete any texts you don't absolutely need to keep.
Delete any emails you don't absolutely need to keep.
Move as many apps as possible to your SD card. No SD card? Go get one.
Move your Contacts and Images to the SD card.
Delete apps you don't want by going to Settings > Apps > then go to each one and choose Uninstall
Yes, all these will free up a lot of space on your phone. The best thing to do is never ever let an app live on your phone unless it refuses to give you an option to go on an SD card.
That will keep your device running lean and mean.