I will try to compress all of it into one post..
First off you will need the Sony Ericsson Theme Creator. The latest version can be downloaded HERE!
You will need some graphics software and the one I think is the best for beginners is Jasc/Corel Paint Shop Pro. Any version above 8 (I use 9). Adobe Photoshop also works but it's far more advanced than Paint Shop Pro and not as easy to get started with. Gimp is another good one and it's free. Use Google as always..
Now you have all that is needed to make a brilliant theme. Only your mind sets the limitations of your creations.
These are just my personal opinions and I'm sure there are themers that disagree with some parts, but these are the most important parts imo:
Tip #1: Make it as functional as possible! Meaning don't use bright backgrounds with bright text. Everything has to be readable throughout the theme. Also, try to avoid too high contrasts in the background image for the navigation screens, because that will make it hard to get a text-color that works on all areas.
Tip #2: Use high quality images. When selecting backgrounds use no highly compressed jpg's and don't use gif at all unless you're animating! And try to use more than one background image in a theme.
Tip #3: Practice! There's no shortcuts to a good theme (unless you steal it..). Practice in your graphics software is an absolute must!
Tip #4: Variation. The key to progress imo! When you think you made a great theme, don't repeat the same process again although this is very common especially with beginners.
Tip #5: Attention to detail. Don't leave anything with a "that will do"-attitude. Make it as good as you can and use this mentality to all parts of the theme.
Tip #6: Research. Just to see what is possible, check some of our great themers threads for inspiration and ideas.
Tip #7: Originality. Make everything yourself! No themers like when people rip their softbars or highlights.
Tip #8: Patience. Both when it comes to the work in your graphics program and in the theme maker. Don't rush it, making a theme will take some time but in the end it will be worth it!
Tip #9: Patience.. Can't have enough of that!
Tip #10: Skill. You'll need some if you want to make really good themes. Photoshop or Paint Shop Pro are recommended since most themers use those programs and tutorials are easy to come by. Things like layers and transparency are things I think you have to know about.
To help out Alien Skin has some really good filters that fits both Photoshop and Paint Shop Pro. Those made by Alien Skin that I use are; Eye Candy 4000, Eye Candy 5: Nature, Eye Candy 5: Impact, Eye Candy 5: Textures and Xenofex.
I have written a few tutorials to guide you step by step:
Making a theme in Paint Shop Pro:
Making a theme preview:
That's it! Now visit some of the threads of the M9-themers and you WILL get inspired! Once you've started making your themes, set up your own thread in the SE section and the comments and suggestions will start pouring in.