There's a great thread in the forums by torstan where he's sharing great tips and tricks. Here's a preview.
This is a non-traditional tutorial thread. I'll be posting little snippets that I originally posted to G+. I'll try to keep an index of the posts at the top for easy and quick reference. We'll see how that goes... These are intended to be entrance level tips that anyone might find useful. Feel free to ask questions about specific topics.
• Drawing top down hills
• City design - start with the roads
• Dungeon design and adventure flow
• Simple hatched city district styles
• Using the Shape Tool to create quick simple icons in Photoshop
• Hand drawn mountains
• Turning a map into an aged paper handout
• A classic gatehouse design for guarding your front door
• Creating isometric dungeon maps
• Quick and Easy Dungeons using Grids
• Using layer styles for attractive dungeons.
• Using paths to create pretty dungeon maps
• Old School Mapping in Photoshop and Maptool
• How to colour a dungeon map.
• Different Tree Styles for Different Battlemaps