I bought an 18" x 24" print. I've never framed anything before, is it as easy as I think it is? Just go to a craft store and pick out a frame in that size?
This largely depends on the value of the print to be honest and if you want to do it "right".
A few things at play with the 18 x 24 off the shelf:
Non-archival backing (acidic, will slowly damage print)
non-UV glass (UV rays will fade print, beware if in direct sunlight, but even floruscent lights will do this over time)
Print touching the glass (some ink will adhere to glass over time, no bueno - this is especially true with metallic inks).
Now, if it's a 30-40 dollar print that you aren't viewing as an investment, probably is ok.
If it's something you want LONG term you may want to find a better solution.
2 options:
DIY - you can go to a place like American Frame and buy the supplies (frame, matte, glass etc) - there are some tools you need. You also could buy a cheap frame from a store and replace some of the pieces of it (ie, add spacers, acid free backing and/or change the glass).
or
Find a non-chain mom-and-pop frame store in your area that does good / cheap work. Something that size without mattes would be 60-65 bucks. Maybe closer to 100 with matting.
good luck