just to add with mcbuffy,
>double push "Home"
-screen @ bottom will pop up
>tab on any icon showing and hold for a few secs.
>hit the delete mark to end that program
to help you save some memory for your other apps.
but if its really slow like very slow to switch to your other screen with others app, then ya, i would restore it.
if you have Jailbroken your Device which means voiding protection plan/etc. , that can also due to the slowness.
so the best you can do if you had jailbroken your ipod touch 4g
(or every ipod) is to restore it and if you open any app and you don't use it then push the homebutton twice and in the lower part of your screen will be a list of opend apps. if there are any apps opend then press and hold the any app a few secs until they are shaking then you see a red close butten hit it to kill the task.
Do it everyday to and your ipod will become faster then now
by the way: If you don't use your ipod as an alarm clock then shut it down to safe more energy and do not charge it to much like oh battery is almoust empty but its only about 50%
if you charge it in the morning for about 2 hours OK but not here a bit there a bit ==> this will kill the batterylife
my ipod touch 4g is killed by this way i tried it out and its true
now i have the ipod touch 5th gen and the ipad mini and 4th gen
I hope my language is ok so you can understand it i often write some rubbish stences