The Oven Mate range is brilliant
For oven shelves try Oven mate just for racks
For hobs try Oven mate Glass and ceramic hob cleaner
For ovens use Oven mate Oven cleaning gel
Be warned, it is a strong chemical, make sure you wear gloves and make sure you wipe it down thoroughly when you've finished.
If you're talking about he horrid brown shiny stuff that gets left behind, you can only remove it with a harsh chemical cleaner like this, nothing else will touch it. If someone suggests using a 'kinder' or 'natural' cleaning agent, and they have one that works, may I suggest that it's not kinder, it's just something that you are accustomed to seeing around the house and it's actually just as aggressive (or otherwise it wouldn't work) - just remember the dirty coin in brown sauce or carbonated drink trick and understand what you're using.