I haven't had to hunt for baby items for years. I think it's the same across the board though as other shopping. First, put out the word that you need stuff; anyone who has had a baby in the last 3 years usually has stuff in their house. Second, check out freecycle, craigslist, ads in the paper, etc. Use caution if you go to meet someone or to check out an item; I never went alone when I did this. Third, check thrift stores. Fourth, don't get stuff you don't need. I paid less than $100 for all the stuff I had for DD when she was born b/c I used lots of methods to acquire what I needed, but I still had stuff that I didn't need or use. Fifth, after you've had a baby shower, if there is one, then you go and get what you need that you still don't have.
Use caution with items you are given. If you don't think it's safe, don't feel bad about getting something that makes you feel more comfortable.
When I think back to DD as a baby, the stuff I needed (truly needed) fit in the diaper bag. I had a changing pad, diapers, a few wipes, a binky, 2 nursing accessories, 2 changes of clothes, 2 toys/books. The only thing that didn't fit was my pump! LOL That was a necessity for me b/c I worked full-time, but wanted to nurse; it was my compromise. We had a crib, but didn't use it until DD was almost 4 months old.
One tip a friend gave me that worked so well was to buy diapers (if you're not using cloth) every time you shop -- around twice a month -- from the start of the 2nd trimester. She told me to focus on sizes 2 & 3 b/c a lot of babies are in and out of size 1 or newborn really fast. She was so right on this. When DD was born I had 8 boxes of diapers, I think. 1 newborn, 1 size 1, several of each sizes 2 & 3. I did not worry the few months about diapers, which was a huge blessing.