I've borrowed so much baby stuff from friends. We didn't need to buy moses basket, crib, swing, walker, steriliser and so many other things. In fact, the crib has been used by around 7 babies!
Bathe the children together, 2 or 3 times a week instead of everyday. I turn most things off at the plug at night and am a stickler for turning thermostat down and lights off. The slow cooker is great too, very economical and I usually just chuck in meat/veg that we have left over.
I often park in town where I can for free and then walk the extra few hundred yards.
I buy lots of toys and books in charity shops.
Freecycle!!