Basically I see that a lot of time, like it's too hard and such... To be honest it's hard only if you don't know what to do.
There's multiple things to consider first... Can you draw a character standing ? Yes ? Good I think you are ready lol I will point you how to do things easily...
1 - Standing character with a normally huge object
That's the easiest to do, draw you character sitting, standing, whatever you want with a monument nearby... You can even find for 3d models on the net, so what are you waiting for ? You don't even need a background seriously, the scene is important as it !
2 - Size difference
This is a bit more complicated but actually doesn't mean you have to draw a background. Draw your character standing and someone else nearby with... a size difference. generally you see his / her face only or half body, still it's important to have one of them fully rendered. You can also draw a part of the body of someone (the end for example) and someone else on it !
3 - Perspective
This is getting more complicated, to be honest I use a 3d software to know how is it on low and high angleview... You will need a background here most of the time, yes... If there's multiple characters it's even harder and of course, if your character is fully standing it's better !
4 - Complex scene
Basically a mix of everything, you draw a background, you show the size difference etc etc... That's the hardest to do and I really don't do that, I most of the time cheat a lot and take some shortcuts...
That's all for now, I don't want to fright people, these are just ideas, of course I skipped all the details, because if you know me, you see what I mean ha haSee ya !