How long to preheat an OTG? I have an Oven Toaster Grill by Oster in 10 litres capacity. I am new to baking and every recipe for egg muffin says you have to preheat the oven but none of them say for how long. This is very confusing baking jargon. So if any recipe calls for preheating, how long should I preheat?

P.S: I know there are similar questions posted but none of them seem to answer in general, they are specific to a recipe (bread/cake et al).
When you set the oven to the required temperature and then close the door and turn it on, pretty soon you will probably see the heating element begin to glow orange from the heat. When the oven is up to the selected temperature, the power to the element should then switch off for a while, and you should be able to see the orange glow diminish and start to fade. That is when the oven is considered "pre-heated". My "big" electric oven (regular size, really) takes about 10 minutes to pre-heat, so your little OTG should be quicker -- maybe 3 to 5 min.(?), but watch the element, or, as Jolenealaska mentions, the indicator light. If it has an indicator light, when the light goes out for a while, it's pre-heated.