Hey guys I just moved into a new apartment and am getting worse wifi reception than in my old place.

I have a run-of-the-mill NetGear wifi router in the room that's going to be the office and then in the living room I have a macmini hooked up to the TV for web browsing etc. The macmini is dropping its connection often and so forth. I think it's because this new place has more walls; my old apartment was a loft, so basically one gigantic room. Also just generally, wifi connectivity to my Windows laptop and iPad, etc. seems worse.

Anyway, I know nothing about this kind of stuff. How do I improve the situation? Should I buy a more fancy wifi router? (if so, which one?) Or get some kind of USB antenna dongle thingie and attach that to the MacMini.

In my experience, the router can make a huge difference. Unfortunately, back in the 802.11g days, even individual units of a specific batch of a specific model of router could vary in their connection quality. That may have improved now that 802.11n is a fairly established thing, but I don't know. I've been running one of the few Linksys models that didn't suck for years, because it actually worked, unlike 99% of the other routers I've used (including other batches of the exact same model and hardware revision, mysteriously enough).

IMO it can't hurt to try and grab a new router.

802.11n is better at passing through walls.

Also, consider if you could locate the router in a different location to minimize impedence of the signal. A few tips:
Avoid placing the router where the signal will have to pass through metal (ie, kitchen appliances) to reach locations you want good connectivity in.
Avoid placing the router where the signal will have to pass through stone (ie, fireplaces, brick walls) to reach locations you want good connectivity in.
Avoid placing the router where the signal will have to pass through walls at an oblique angle in order to reach locations you want good connectivity in.
Try to place the router in a high place, there's typically less stuff going on above chest-height or so (ie, no furniture, fewer appliances, chimney but no fireplace.)
Consider purchasing range-boosting antennae for the router or receivers if your hardware supports it. You can also get antennas which are at the end of a flexible wire, which might give you more freedom in placing it when the equipment in question can't be moved.
Consider a wireless repeater, and placing it in a location with good line-of-sight to the router and areas that you want good connectivity in. If your router has wired ports, and you can run a wire (you can usually tuck them under baseboard molding, or sometimes the carpet itself), you can wire a secondary router/wireless switch to cover under-serviced areas.

802.11n is better at passing through walls.

Maybe.. If you're running 802.11n on 5Ghz alone, it will likely be worse through walls. If you're running it in dual frequency mode (MIMO) (2.4Ghz and 5ghz) then you may notice an increase in penetration.

USB antenna dongle thingie and attach that to the MacMini.

Maybe also get a directional antenna. It did the trick for me.

How does your cell phone work in the place? I ask because we lived in a pretty new ~1000 sq ft apartment once that literally ate the wireless signals. It was a giant Faraday cage basically, because the walls were lined with some bizarre type of metal studs. We got maybe 11mbp/s on the WiFi, if we were lucky, and we had to go outside to use the phone every single time. Both of our phones were affected. Oh yes, fun times when it was -30C and windy LOL. Of course, the landlords didn't advertise this before we signed the lease. I feel your pain. Maybe see if other tenants have the same grief, and if so, maybe do something about it so that other people won't be tricked (misinformed by the landlords) in the future.

In terms of the house that I live at now, I can connect to the neighbour's WiFi at reliable rates generally faster than 11 mbp/s, but of course not usually full 54mbp/s. I'm on a computer upstairs on the northeast side of the house, and their WiFi box is downstairs on the southwest side of their house. So yeah. A wall/floor or six shouldn't totally kill your WiFi, unless it's lined with some bizarre type of metal studs. These houses were built in the mid-70s, so it's definitely wood studs, and you can tell.

Very dumb question: Does your router have a detachable antena, and have you tried checking that it is properly connected?

A classmate once spent several hours 'troubleshooting' his router that worked perfectly before he moved across town. Ended up just being the connectors were unscrewed.