Please need help regarding diagrams..

[antoun]

Hey there everyone I've been on SSP for almost 10 years now I really love it its the best ! I've always wanted to draw structures especially undrawn but never really found a suitable program for me to draw. If I was to draw my main is to make the drawing as realistic as possible. Please can you guys help me out here? maybe some advice on the best programs and some tips on how you use them... I hope I can get some feedback would be great