Not something the Pi does well, but it can still be improved. Firstly Midori is not a bad browser, but Iceape will probably be better. It is less intensive, and has an adblocker which is pretty damn handy given the state of the web these days. You can even switch off java and images to save bandwidth / processing power.
Step 1: sudo apt-get install iceape
That's it, iceape is now installed. I recommend the adblockplus plugin as a bare minimum
Step 2: Go to 'Tools>Add-ons Manager and search for adblock. When it comes up click on the install button. You'll need to restart the browser to make it work.
If you think you'll need flash then I recommend gnash (an open source alternative):
Step 3: sudo apt-get install browser-plugin-gnash
Don't try and view / play anything too big though - the RPi's not built for it. Youtube is still a big fail. Sorry.