You can try by learning the basic scale the Major Scale which is technically a Do Re Mi Fa Sol La Ti Do!!! start by playing a note let say a D on the A string that is your Do the E note is Re and so on....you can play this over the key of D (root chord) or Bm (relative minor) you just have to adjust it if you're using a different key..... I can't say that my method was right but hey..it worked for me!!