I just have a few tips for you, because I am no that professional into designing. (not in specific orders and some of them may seem stray :/)
1. Use helpful 3D graphing tools such as "Blender" to create a sketch of what your desired plane would look like.
2. Find a suitable airfoil for your airplane, maybe at airfoiltools.com.
3. Build parts of different scales for the first plane, so it would be easy to make changes and adjustments, such as the vertical stabilizer is not doing its job.
4. Test fly a ton.
5. Try new stuffs. Maybe like me, using sanded, bent cardboard paper to cover up the edgy foam board fuselage (getting a smooth and round airframe from foam board is just too hard) and it worked out perfect both visually and aerodynamically.
If you're interested in the aerodynamics and science of designing your own planes, There are three books by Andy Lennon you may want to check out. Specifically "RC Model Airplane Design" has a lot of great information presented in a way that we mere mortals can understand.
I have always used the TLAR (that looks about right) approach with limited success but enjoyed every project I've tried.
you can watch other people design their planes first, like example,from Flitetest. i admire their plans a lot as their plans are very well designed. i believe that by looking through their plans, you will get a better idea of how to design your own plane and how will the end product look like.
Good luck designing your plane.