Help with 300dpi

I feel kind of embarrassed to ask this question because I have been using PhotoShop for quite some time.
However, I have been doing only web-based graphics and I never cared about printing and about the technical stuff behind printing.
I don't even have a printer, it's that bad.

Now, my problem is that I want to send a graphic file to somebody and they require it to be 300dpi, so to be able to print it.
So, I just upped the dpi of the image document to 300 and it got scaled up and became blurry (which is normal and I have no problem with that).
So far so good...

The problem is that when I rick click and do "Print Size", to preview the file in its actual size, it looks blurrier than before the stretch!

I mean, obviously it's normal for the image to become blurry when you preview it stretched out, but why does the it look blurry in its Print Size too? :confused::confused::confused:
Isn't it supposed to go back to its original quality when PhotoShop shrinks it down for a "Print Size" preview?
I assume it will appear blurry on the print paper too.
Is there a way to fix that? I just need a quick fix (if there is one).

Thank you very much!

sounds like you saved it as low resolution then are trying to increase size from that.......not gonna happen very well

iDad said:

sounds like you saved it as low resolution then are trying to increase size from that.......not gonna happen very well

Not sure what you mean... :confused:
It's a 72 that I stretched out to 300 dpi.
However when I shrink the 300 dpi down for a Print Preview, it is a bit blurry, even when it is shrunken down to its previous dimensions.

What should I do to avoid this?

^ Say what? :eek: