If you'd like to add photos to your posts that display as full images (rather than attachments that need to be clicked on to view), the easiest/best way to do it is by using an image hosting account like Photobucket or ImageShack.
I use Photobucket because it's quick and easy. Here's a tutorial on how to use it:
1. Sign up for a free Photobucket account:
http://register.photobucket.com/2. Upload your photos.
If your photos are larger than 640px across, please make sure "640 x 480 (Large")" is selected from the "Reduce to" drop-down menu. This will automatically resize the image.
3. Mouse over the photo you would like to add to your forum post.
This will bring up a small window below the photo that contains various link options. Click anywhere inside the "IMG Code" field. The text will be highlighted and a quick "Copied" notification will appear.
4. Paste the code (Ctrl + V or right-click -> Paste) into your forum post.
The necessary IMG tags are automatically inserted for you.
5. Repeat as needed. If you need to add more photos, you may do so in another post.
And that's it.
The benefit of using an image hosting service like Photobucket is that the files aren't being stored on the server. This helps to reduce bandwidth usage and load times.