Okay, so here's where I act like I know everything about flyers. I don't and am a pompous asshole, but some of this may be useful to you:
If you have no budget, go easy on ink/toner and definitely stick to black and white. That means white backgrounds wherever possible and light images.
If you're only paying per-page, stick to black and white but feel free to waste their ink with big black/dark gray sections as needed.
Full sheet things are a waste of everyone's time and money unless you're posting them on bus stops or something.
Jesus people love the quartersheet sized booklet. I can give you a photoshop, pdf, or indesign template for making those, but they're pretty easy.
Double sided printing is the best thing ever. Especially if you have someone else figuring out how to get the fucking duplex shit to work right.