Questions regarding printing

Sorry if this has been covered before but I've been getting some nice feedback with a few smoke photos I've taken and one of my friends wanted me to blow one up for her.

I'm probably going to take it to a photo processing store but before I do that, what is the best file and settings I can use to optimize for printing? It'd most likely be around an 11x17.

Also, is there some other tips and tricks I can do with my photo to make sure it comes out well? I'm quite nervous because I've never printed anything of mine before lol.

I do have a Epson Stylus Pro 3880 at work that's not in use I'm trying to take home (family business). Hopefully I can do some persuading to let me "borrow" the printer.

11x17 is an odd size, most consumer labs won't do it. They will do 11x14, which means that you will have to crop off some of the long side. Some labs may do 12x18 which would be the same aspect ratio as the native image. For 12x18 at 300 ppi (the recommended resolution) you will need 3600 x 5400 pixels. You can either let the lab handle the resizing, most do it well, or you can resize it yourself followed by sharpening to taste. Be sure the image is in the sRGB color space. Beyond that, you should be aware that if your monitor is not calibrated and you are not working in a color managed application, what actually comes back from the lab will be a matter of luck.

Thanks tzal. Should I do JPEG or TIFF when I put it on a disc for them?

On a disc, since size is not a consideration, I'd leave it in tif. But if uploading to an on-line lab, a high quality, one save jpg is not going to do any visible damage.

Thanks a bunch!