How do people make those nice-looking icons?

I tried to make one in Paint.NET, but I pretty much failed at trying it. Other people have nice ones like that Remington 700 and Chad’s weapons. How do I do it?

Stuff like Photoshop, or other Adobe products, if your low on money, GIMP is one good free one.

Edit: Also, good pictures can come from lots of experience.

I always thought those icons were a part of a pack, because I remember Garry saying something like making icons for bouncy balls. I’m pretty sure he also made a icon of the same ‘blue background, white outline’ for his first test of the bowling ball download.

Photoshop or paint.net