Engine is misfiring?

Engine Mechanical problem
2003 Nissan Altima 4 cyl Automatic 170000 miles

I have a cylinder misfiring and it is making my drives a real pain. I want to get it fixed, so what do I need to know so that I don't get ripped off by the mechanic?

The most likely cause is a bad coil. Is your check engine light on? If so, find out which cylinder is misfiring by having the codes scanned.

P0300 (multiple cylinder misfire)
P0301 (1st cylinder misfire)
P0302 (2nd cylinder misfire)
P0303 (3rd cylinder misfire)
P0304 (4th cylinder misfire)

You can verify that the coil is bad by disconnecting the electrical plug/connector that connects to the coil one by one. As soon as you start pulling the connector off the coil, the engine should start studdering. When you come across a the coil that makes no change to the engine when you disconnect it you've found your culprit. The coils will set you back about $70-90 each. I would advise changing the spark plugs out at the same time, just in case any of them were fouled out by the misfires. FYI, Nissan uses NGK PLFR5A-11 plugs. (The 11 at the end means that they're pre-gapped to the manufacturer's.043mm, so you won't need to regap them.)