as far just making stuff up . I just sit down with my guitar and play around till i find a little groove pattern somthing that is easier to follow . Then i'll add a progression up to a higher note then the next time i play the beggining groove i'll add a lower part . Sort of like steve vai's Kim-pee-du-wi .
If not that way i'll find two cords i like and then add in some little fill scale type runs inbetween . Racer-x's addidcted to that rush is a good example of what i try to do with this approch .
If i am trying to focus more on cords , I'll again find a nice cord alternate pick it and then find another cord in the same key .
I dont worrie much about keys or what notes fit as much as how it sounds , I'll find a scale or mode that fits the progression's key and go from there . I am newer to the hole theory thing though , so i am sure that more advanced players can offer better solutions to ear theory training .
As far as expansion on creating a solo that has melody , i advise you to listen to a lot of different players . All sort of have thier own individual approach to how a solo's melody should come out .
My favorite players to listen to solo are
steve vai
joe satriani
greg howe
paul gilbert
there are plenty of other players out there but those are a few of my favorite
And as far as just doing crazy stuff on guitar
steve vai
Micheal angelo balto
and Bob zubec (i just found out about him and i like his style a lot ) here are some of his clips .
http://www.youtube.com/w/Bob-Zabek--...ch=bob%20zabek
http://www.youtube.com/w/Bob-Zabek--...ch=bob%20zabek
http://www.youtube.com/w/Bob-Zabek--...ch=bob%20zabek
Racer-x 's addidected to that rush
http://www.youtube.com/w/Paul-Gilber...paul%20gilbert