How do I make a postcard?
I use my word processing program...under labels. But you can just take a sheet of 8.5 x 11 cardstock and cut it fourths. Each piece is a post card legal size. I put the entire sheet (page 1) in my printer and use my computer graphics to print something cute or noteworthy on each one - individually or as a group. I also type three lines on the reverse side (page 2) for writing the address. This is not necessary, but let's people I am gifting with the post cards know what they are to be used for. Then just print and cut apart - usually 4.25 x 5.50. Put proper postage on 'em and mail.
Here is what I do. I go the thrift shop and buy old post cards and redecorate the front with what ever I want. Most of the time you can buy a box 50 for about 50 cents.
Another way would be to get some cardstock cut it into fours and decorate your way. There are also free programs that will let you print on one side the look of a post card.