How to convert a 72 dpi image to a 300 dpi image and making it better quality for print?

You, basically, can't do it, for the reasons a couple of people, here, have mentioned. You cannot add "information" to an image that did not have it to start with. ( I have already offered a brief explanation in my answer to your other, camera question) However, all is not completely lost. You CAN, kind of "fake it" by some carful manipulation of the image. You can slighty improve the image for printing to a higher resolution, but not by very much. In Photoshop, under the "Image" menu, select "image size." Go ahead and increase the resolution and set the image size to what you want. REMEMBER, don't expect too much improvement, so don't increase either of these numbers too much. In other words, dont expect good results if you select 300 DPI and expect an 8 by 10 print. This will result in what looks like larger, blockier pixels. What happens is that where each pixel had it's own color, this adjustment created larger blocks of color, made up of several pixels. Then, in the "filters"menu, select "noise" and then "add noise." Set the percentage to somewhere between 5% and 10 %. Too much will defeat your purpose, which is some improvement in image quality. What this does is randomly change some of the colors in those larger blocks, breaking them up slightly. Next, in the "filters" menu, select "blur" and then, "blur" again. This will blend in some of the random pixel colors you created in the "noise" function. The result will be a slightly out of focus image. Finally, in the "filters" menu, select "sharpen" and then "sharpen" edges. This should lessen the effect of the "out of focus" effect created in the previous step. This whole process takes some trial and error experimentation to get any reasonable results. The key is to make VERY small changes at each step. Some times you have to repeat these step a few times. Sometimes you may have to go back and start some or all of this process all over. In any case, you should not expect a miraculous improvement of picture quality. What you CAN get is a slightly improved DPI that has a less "pixelated" quality. Good luck, and have fun with it.

It is a damn good question!!!

You can do it in Photoshop, but this is not going to make the photo any better. If the original photo is lacking in detail and resolution, going into photoshop to interpolate the image will not give the photo what it didn't have. If you want to experiment for yourself simply open the image in Photoshop go to edit > image size, highlight the dpi and type in 300. It will almost certainly result in a muddy looking image.

lol... ok, so you need the phot to be 300 or better for printing, like i said in another answer, if your printing from home, use Photoshop to make it 300 DPI, if your sending it to a printing place, send it at the size (dimensions) you want, ei, 4x6, 8x10... leave the dpi @ 72 and the print shop will take care of it, raising the dpi to their printers native size. I know some printers like my old Epson would only print good at 360dpi, yet my newer HP will punch out a great photo at 200 or even 100 DPI.. it might be worth it if your printing at home to find your printers native dpi count.