What type of printing will you be doing?
This will hopefully tell me whether inkjet or laser jet will be the best option for you. If its for home use and you will be printing photos and very small amount of printing, the I would recommend an inkjet printer. On the other have if you printing text and quite a lot then laser would be the best option.
Print , Copy, Scan, Fax
There are so many printers that now come with these options. Gone are the days where you would have a separate printer and fax machine, now it is all in one unit if you like. If you only want a printer then that's fine, but purchasing a multi-function device could save you headaches in the future.
Mono and Colour
I would say that 90% of our printer sales are colour devices however printing colour is great, but also a costly exercise. Even if you are only printing black, your colour levels will still decrease over time and unfortunately you will need to purchase the colour toners which may be a similar price to what you paid for the machine itself. However in saying that, it never been so cost effective to print colour in recent times.
In summary, with printers, you get what you pay for. The less you spend, then you only get an entry level printer which will cost you a small fortune to print. Here is an example. You can purchase a cheap mono laser printer these days for $60 and the cartridges will cost about $80 and will last about 1,500 pages. Compare this to a better printer which will be faster an possibly be wireless and will cost around $350, the toner will now cost about $90 but will last for 2,500 pages. Even if you're a small user and only go through 5 boxes of paper a year, it will cost you about $660 a year in toners compared to $450 in toner on the more expensive printer. Over 3 years your will be well and truly better off with the initial outlay of $350 instead of $60.
The general rule of thumb is that the more you spend on a printer, the better the running costs and the less it will cost you in the long term. However it is all relative on how much you are printing.