A printer is asking for a 300 dpi jpeg. I have set the image size to the correct printing size but what resolution do I set the ppi in photoshopCS2 to for 300 dpi. Also when saving a jpeg there is a box at the bottom saying Size which is 56.6 Kbps do I need to change this as it doesn't seem to change the image size?
PPI means "pixels per inch," and is a web display measurement.
DPI means "dots per inch," and is a print measurement.
If your Image Size dialog box reads "300 pixels per inch," you're fine. However, if you're starting at less than that, most likely you cannot arbitrarily make the PPI larger without sacrificing quality. (Depends on how far you're sampling up and what the image is. 266 → 300: probably okay. 72 → 300: ain't gonna happen.)
When you're saving the JPG for print, you shouldn't be using the Save for Web option. That's why you're getting the modem speed. That number (56.6Kpbs) is telling you "this is how many seconds your image will take to download to the user's browser at this given speed." It's not relevant to you in this context. Use Save As instead.
@Lauren Ipsum - great answer. I would add the following basic advice since you are new (to print): - Preview /convert your image to CMYK colour gamut as I suspect you are in RGB. Although RGB is best for correction, initial editing and screen/web work, CMYK represents the four plates of process printing = Cyan, Magenta, Yellow, Black which will make up your printed image. Typically RGB has a wider range so the colour WILL CHANGE at the printers if they convert it from RGB to CMYK for you. Best to keep this under your own control. Note: even if your printer has some form of digital press, the printing industry understands CMYK and Pantone* more than RGB in my experience - they may / or may not have a Mac and reprographics professionals at the printers end to optimise conversion - don't assume they do (or that they have the latest software - I have seen printers run jobs through multiple software, hardware and even operating systems before going to press.
On that last point it's a good idea to ALWAYS get a printed proof (ideally on final paper) from the printer before you commit them to a large run (and you can ask to be there and check it on press if you are still concerned).
- Pantone is an accepted printer's ink mixing / colour swatch system which guarantees consistent colour - most often used for brand colours and tricky process colours such as bright orange or reflex blue.
I am surprised that your printer has asked for a JPEG file as this is a compressed format - any compression deteriorates the image. For print I use 300 dpi CMYK EPS files into Indesign for layout and then pre-flight / output a press ready PDF for the printer. If this is a little too advanced for your needs, I would send them an EPS or a TIF image on a CD / Flash drive without compression. Or Dropbox it to them over the web.
Any fonts within your file should be converted to paths (Indesign) or bitmapped in Photoshop to prevent them changing at the printers end which can happen if they don't use exactly the same foundry / font as on your own PC. For example Helvetica on a Macintosh (a system font) which is not the same as Helvetica from Bitstream or other vendor, which the printer probably has installed (likely they have half a dozen different versions of this particular font - Microsoft ship one as well).
Lastly, if you are unsure, ask the printer for their preferred file delivery specification. It's in their interest to help you as it saves them time and groans in pre-press. They should be able to email you this as a single A4 sheet PDF. This helped me a good deal when I started with new challenges, e.g. creating retail packaging for a client in another country printed in China... (I never actually met the client or spoke to the printer) and DVD pressing / packaging through Eastern Europe - all done via FTP. Those were the days.
Good luck with it.