Start with budget then what it's going to be used for. Typing up homework? Just looking things up without creating anything on it? How big do you want it? For use more like a laptop, you'd want a 10" screen or so, not the smaller 7" ones.
Android tablets are generally good for "consuming content" like reading / watching videos, however, they are not really good at creating content / doing homework.
$300 is rather low for anything larger than a 7" or 8" tablet unless you are considering used / refurbished tablets.
The recent release of Intel's Bay Trail generation Atom processor has also meant the release of new 8" Windows 8.1 tablets for $300 or less due to holiday sales. One seemingly popular Windows 8 tablet is the Dell Venue 8 Pro. This the full version of Windows 8, not a cut down version of like Windows RT. Additionally, all Windows 8 tablet should come with a free product for the Home / Student version of MS Office 2013.
At it's core, these Windows 8 tablets are like mini portable entry level computers. They can be connected to keyboards / mice / monitors but you need to buy additional equipment to do so. Also it comes with a digitizer, which means with a Dell digital pen (extra $40 - $50) you draw / paint / write notes.