1. A flat yard is not that important if the yard is small or not incredibly steep. A mild slope is easy to mow. I have a loped lot and it's a pain in the butt, but the yard is huge, and I'm just getting too old to mow a sloped 1/2 acre, but we've dug up grass and planted bushes, etc, which don't require mowing. There are also varieties of grass which are low growing and slow growing and drought tolerant...A steep driveway can be a major pain, especially on ice or snow.
2. I like searching via Redfin. The maps are friendly. If you specify size and price, you can narrow it down geographically.
3. I take notes. I look for things I don't like, especially things that are going to cost a lot of money because they're necessary as opposed to something cosmetic. I also write down how a house feels and whether it's professionally staged, etc. Compare size, lot size, etc, whether it meets the criteria you're looking for...Sometimes that criteria changes as the searching process progresses.
3. Don't take advice from strangers if they're going to profit from the advice they're giving. Listen to their advice either if they have no vested interest OR the advice they give will not potentially reward them. I've followed my gut before, but afterwards realized I was falling for cute staging and it wasn't my gut. My gut was telling me to eat pizza but I thought it was telling me to make an offer on a house...So maybe don't go house hunting while hungry?