As always, determine how much you want to spend on a copier. The price range can go from a basic desktop model for $300 to over $100,000 for efficient, high volume production.
First determine if you need a color copier or if the majority of your output is black and white text. You can purchase a laser black and white copier relatively inexpensively, and contract out the occasional color job. However, if budget allows, an inkjet color copier will give you flexibility and keep you from running to the print shop for every color copy.
How many copies will you be making per month? Look at the counter in your current copier (usually under the glass platen) for an estimate or check your copying bills to get an idea of past copier needs. If you expect high volume use, look for a larger, sturdier copier. These copiers take up more space and the initial investment is higher but in the long run, these models can take the traffic and are cost efficient.
Copiers are rated by the number of pages of 8.5 by 11 copies per minute (cpm or ppm) they are able to produce. If you do a lot of single copy work, make sure you find out the time it takes for that initial copy to print.
If you do a lot of multi-page copying, look for a document feeder. Rather than placing each page on the glass and lowering the cover, the copier automatically feeds the stack.
Do you do significant two sided copying? You may want to look into the pricey RADF or recirculating automatic document feeder. With this option the copier can flip the page internally, making two-sided copies from two-sided originals.
If you need multi page reports for your staff or clients, collating capabilities may be appealing.
Do you use a variety of paper stock, both in size and quality? Most larger copiers have paper trays to accommodate differing sizes so you aren't constantly changing paper.
If you frequently use heavier paper stock you will need a stackable bypass tray to avoid frequent jams.
These needs will be reflected in the versatility of the machine and therefore the initial cost.