There are two way to restart an ipad, a soft method
1 - press and hold the top button and then swipe to power off (this will gracefully put it into hybernation)
2 - press and hold the top button and the home button to reset (this is an ungraceful way to restart the device and may forget last things you have done).
the best option is always to go to the multitasking page (double tap the home button), then press and hold one of the icons till they start wiggling, then tap on all the minus signs in the little red circle, untill all the apps have been unloaded from memory, then do a press and hold then slide to power off.
This method is least likely to cause corruption on your device.
With Safari on your device, make sure your not always having the maximum number of webpages open, you can see this by the numbers circle icon on the page.
You will only be able to open a maximum of 9 seperate pages at one time, and each page will increase the memory requirement of the app.
I have found keeping the number of pages open down increase the speed of safari aswell.
To close them you can tap on the numbered icon and then you can tap on the x in the red circle to close that page (tab if you like).