For writing, I find ideas in walking. Simply that, walking. Not turning round and around in my home, mind you, but walking in the street: once I reach my "cruising speed" pictures of events and characters come to my mind, so I watch them doing their stuff and listen to them saying their dialog, and I try to remember the most of them, even if I know that they'll change, and often heavily, when I'll write them down. Sometimes, just remembering the mood of the scene is enough.
Rimbaud used a similar technique, this is why his verses echo the rythm of his own steps – but of course I ignored this when I began my walking dreams, back during my childhood...
As for drawing... Well, I'm rather the pragmatical/realistic type so I tend to build things according to real constraints; for having a background in industrial design and architecture, I know one thing or two about constructing objects and buildings and this gives me a method. The downside is that the result often is very functional and lacks of soul: that's when references come in handy, to populate the insides or decorate the outsides; also, thinking about who live in the house or what sort of people work on the scene helps to give me ideas about such details. Because I suck big hairy balls at characters, except maybe mechanical ones, I do not do this kind of stuff.
In my opinion, block comes mainly from our own limits. Because we don't know how to do something, or fear we're on the wrong way, or whatever reason. Therefore it's always a good thing to have some database of books, paintings, photos, but also movies, comics, songs/music, etc.: anything helps finding ideas – sometimes I even find myself in the position where I have to make a choice beween far too much numerous ideas

Because, let's face it, none of us invent anything, even the most brilliant creators: we all recycle old things in one way or another, finding new things only by mistake and without even realizing it until someone puts our nose into it...
This is why a creation reflects the mind of its author, like some sort of a photograph of a moment of his life, but that may be an entirely different debate.