I've found that baking soda mixed with a little water (to make a paste) works well, to help with scrubbing. Then just rinse thoroughly. I prefer that to harsh chemicals.

But one thing I strongly suggest is to always read the oven's manual, regarding what the manufacturer suggests for cleaning. (Usually the manual can even be found online, and in English).

We recently moved into a new apartment, and when I went to use the oven for the first time, I noticed a really awful chemical smell coming from it, as it began to heat up. As it turns out, the woman that lived here before us didn't read the manual for the oven and used a commercial/chemical oven cleaner in it, when she shouldn't have. It took a long time for that disgusting chemical smell to finally go away. It was so awful I didn't even want to eat anything cooked in there until the smell was completely gone.