These are the reasons why I started making cards digitally:
1.  The prices of greeting cards make me laugh out loud (and then cringe.)
2.  It's hard to find the perfect card for each person, especially being time crunched and standing there in the greeting card aisle as Jake tugs at me and the people around me annoy the heck out of me.
3.  People know I'm creative, and they kind of expect something creative from me for cards.
4.  I made cards for a while with my paper scrapbooking supplies, but I'm super-stingy with supplies and it broke my heart to use good paper or stickers on a project I didn't get to keep!
5.  AND when I made cards with paper, supposedly using "leftover scraps" from other layouts -- I could never find the right sized scraps and I got so tired of having scraps everywhere and saving them just because I *might* use them on a card someday.  Not to mention the time it took to assemble the cards and how small most of the elements were.  (I don't think it's fun trying to get liquid glue on a 1/4 inch in diameter flower!)  And if I wanted 5 of the same card I had to start from scratch each time!  Yuck!
6.  It's more fun to give someone a card that's PERSONAL and has EXACTLY what I want it to say.
7.  There's all these cool digi-kits I'll never have time to make LOs with!  I can use lots of different kits for cards, which are SMALL projects and easy to tackle when I feel overwhelmed
8.  'Cause I can.

It's really easy to make cards with digital elements, and SO much fun!

First, pick the dimension you want the card to be when all is said and done.  Open a new workspace to play in, and start dragging and dropping!  You can make a traditional card, or use all your Photoshop knowledge to make something really funky!  You can personalize it with a photo, or just use all the cool elements in a kit (or mix and match elements from multiple kits). 

I like to create one design, save it, and then use variations of it for different occasions.  This "3 years!" card I used for one of my son's friend's birthday, as well as for an anniversary card.  I also took off the "3 years" and replaced it with "Dad!" using the same letter elements for a Father's Day card for my dad!  (Elements for this card are from Shabby Princess' freebie Shabby Smiles kit.)

To mount (now these directions are for paper scrapping -- you know, sitting down at a table instead of a computer?  Click on the image, which goes along with these directions, to view bigger):
1.  Trim white border from photo card.
2.  Find cardstock color that coordinates with your card.  I'm using brown in this example.  Reasonably priced cardstock can be found at Michael's.  Don't buy the kind that costs a dollar a sheet.  I personally think it's a waste of money.  Yeah, I said it.  What.  You wanna rumble?
3.  Using double-sided tape or your preferred adhesive, mount photo card in the bottom corner of the cardstock, leaving a photo sized space of cardstock above the photo (see image.)
4.  Using a handy-dandy paper-cutter (read more from me about paper-cutters by clicking here), cut the remaining cardstock on the vertical side of your card (in this case, cut to the left of the card.  Where there's a red line.)  Leave that cardstock above your card as is!  You need that to be the middle of your card!
5.  Still with the paper-cutter, but using the scoring edge (the black piece), line up the top of the card and score a line to use as a fold guide.  (In the example, where there's a yellow line.
6.  Fold on the scored edge -- you may need to trim the folded side of the card to match up with the bottom of the front.
7.  Write something in the middle, and you're good to go!