What model of laptop is it? How much memory does it have now? You'll need to find this out if you are to upgrade it's RAM. If you're low on RAM thus use a lot of virtual memory adding more will certainly boost performance.
Read about virtual memory here:
http://www.laptopmemo...system-memory-matters
This may also be worth a read:
http://www.laptopmemo...memory-upgrades-guide
Defragging the hard drive only provides so much a boost, I would consider replacing the hard drive. Again, you need to find out whether it uses a IDE/ATA or SATA interface.
What OS is it running? Windows XP and Windows 7 are the fastest, use these respectively depending on whether your laptop is older (i.e. pre 2005) or newer.
You may also be able to upgrade the processor in your laptop but this is more advanced and you need to take into account various factors. Best to leave this option last.