Here is a little tutorial on the process I used to create a watermark for myself. Now, I'm not very savvy on these kinds of things but it worked. If you know of an easier way, please share. :) Its really not that difficult though. Once I figured it out (which took me For-evah!) it takes little time to repeat the process. So, here goes:
In Photoshop you'll need to create a New blank doc, name it and then choose "transparent" at the background contents area.
You will get a blank "checker board" looking document...so far, so good. Now, lets make it pretty.
On the right of your workspace you will find your edits for your content. Select a graphic you like and add it to your workspace (blank layer) by dragging it over. Or, you can choose it and then click "Apply".
Once your graphic is there you can adust the size, angle and play around with it until you like it. Click apply (in my case the little green check mark).
Add more graphics if you like to create a nice visual for your watermark.
On the left you'll find the "T" in the tool bar. Click it and add your text box in its desired location. (Remember you can move it later if you need to.)
You can fit all of your text in one box. However, I find it easier if you use more than one:
Using more than one box allows you to adjust font style and font size more easily. Also, it allows for easier positioning of your text.
Note the highlighted box at the top, this is your font color. Most programs default to a black. You can choose what color will work best for your projects. In my experience with watermarks a lighter color actually works better.
Here is what the font and color look like after the adjustments.
Now, we save...
First, go to the "Layer" key and click. On the drop down box choose the "Merge Visible" option. (Its near the bottom of the box.)
Now, you want to save as a PNG. file. On the options be sure that "None" is selected and click OK.
Here is a photo of a card I made. The watermark is on the lower left corner.
So the mark is visible but not too distracting.
Have fun with this. If you need help applying the watermark to your projects let me know. I'll help set up a tutorial on how I do that too.