One thing we remind all of our clients to do is to watermark their images with their domain name before they post them on social media. Watermarking your images will do the following:
Prevent unauthorized use of your pictures: If you don't watermark your images and are posting them on social media, don't be surprised to find your picture on a Facebook advertisement for a dating website along with the caption "find single horny girls". We've also seen entire fake Facebook profiles created with un-watermarked images. These profiles were used (often successfully) to scam people for money.
Tells/reminds people where to get more: You are in this business to ultimately make money. It's difficult to make money from your social media if people can't find you and have no idea you have a website. If your picture is watermarked, viewers will be able to visit your site directly, where you'll then have the opportunity to convert them into paying members.
Don't feel bad about it: Again, this is a business. Anyone who has a problem with you watermarking your images is probably too cheap to pay for a membership anyway. If they like what they see, they will be grateful your images are watermarked so they know where to get more!
Choose a simple font: Use a simple non-script font with large letters that can be easily read. If your domain name is not legible, there is no point having a watermark at all.
Use your full web address: You are ultimately trying to funnel viewers to your website (and then to your sign up form). Give it to them straight.
Place the watermark over your body horizontally: Placing the watermark over your body will prevent the watermark from being cropped out. Also place the watermark horizontally so people can read it. Running it artfully up your leg does not help legibility.
Watermark on your phone: If your watermarking tool is easily available on your phone, you're much more likely to continue doing it.
Find an app
iPhone: Here are some of the iPhone apps that current clients have used and have liked:
Marksta: $2 - Customize your watermark by choosing from various fonts, colors, sizes, and and even adjust opacity and drop shadows: itunes.apple.com/us/app/marksta/id589118011?mt=8
iWatermark: $2 - Offers the ability to upload your own watermark image: itunes.apple.com/ca/app/iwatermark/id357577420?mt=8
BeFunky: Free - Easy watermarking features along with other options: itunes.apple.com/ca/app/befunky-photo-editor-for-ipad/id493005926?mt=8
Photo Impression: $2 - Simple but good.: itunes.apple.com/ca/app/impression/id364597384?mt=8
Here is a search on appcrawler.com for more watermarking apps for the iPhone: appcrawlr.com/app/search?_src=sort_&max=12&q=watermarking+photos&query=best-apps-watermarking-photos&prefix=top-apps&price=&device=iphone&sort=&trigger=deviceChange
Add Watermark: $2.61 - Add watermarks to your pictures. Put your property text or a logo image into your picture, adjust its size, transparency, rotation, alignment, then save and share it. Lots of settings and features, also auto processing and batch mode: play.google.com/store/apps/details?id=com.androidvilla.addwatermark&hl=en
There are also many other watermarking apps available for the Android. appcrawler will show you several good options: appcrawlr.com/app/search?go=go&q=watermark+photos&device=android
Here's a great example of a simple, easy-to-read watermark that will definitely drive traffic.