UPDATE: I got the photo printed over at the local FedEX office store. They have a big Canon plotter that did a decent enough job of it. I mainly wanted to see how well it would turn out given the file size. The print is 24x18, and as the Asst Mgr said you can read US NAVY on the planes, so I'm pretty happy. It wasn't the best exposure but that can be improved on with practice. I was mainly interested in seeing if I needed to invest in a higher resolution camera to get acceptable prints. I think more practice with the cameras I have is what will improve the print quality of the images.
This is the file I had printed:
FE 24-105mm F4 G OSS
+1 to what bdbits said - your printer (or driver) should have a "printer check" function and a "clean nozzles" function. Run the printer check and look at the output vs. what it should look like and if it doesn't look right, run the clean nozzle and then printer check again, repeat until the printer check looks good.
I print infrequently so I have to do the above all the time ...
Forget the MP. When you're printing you need to worry about DPI. I always save RAW files to 300DPI. I have enlarged 20MP shots from M-4/3 to 24 x 30 and they turn out beautiful. I've enlarged 180DPI 6MP shots from a Kodak Easy Share to 8 x 10 no problem.
Do not take it to Office Max, they're not set up for photos. Upload it to NationsPhoto:
They will print it on actual photo paper. They do high-quality work and is the only place I use anymore. Their prices are great too. I have bought 8 x 10's for as low as $0.89 each. Get on their mailing list, they have a sale about ever two weeks.
If your photo resolution is too low they will warn you when you upload. Even at that I've went ahead an printed up to 11 x 14 with the warning and was still happy with the results.