Something problematic at house sites are old nails. They can help you find the building, but unless they're something like handmade nails, completely unremarkable, and I think could mask other items.
Noticed there's pointer detectors now. Considering the time I've spent sifting through a pile of dirt to find a small item, they look like they'd be worth it.
Around old house sites with tons of iron in the ground, a small coil helps a lot. I have 5" "hockey puck" coils for every detector I own. The aftermarket 5" coil on my Eurotek Pro never comes off, as a matter of fact. That detector has a super fast response time, plus with the adjustable iron volume, it does really well for me in iron-laden sites. I have mine set up to cherry-pick coins out of trashy areas, and it excels in that role.
If you don't have a pinpointer, you really, really need to try one. I wouldn't hunt without one, they are that handy.