Dearest Martti, Mogram knows how to ballpoint pen! Tips, yaay
I would recommend first working out which bits of the picture need to be darky shaded looking, and which need to be light and detailed-y. Leave the latter, don't go overboard shading them! Or it turns into a mushy blob of Biro ink. However, for those dark shady bits, crosshatch them! You can't change the line colour or thickness with Biro, but you can change how many lines you put on there! Crosshatching is very useful.
Hooray for tips! Tune in next time. I hope you found that somewhat useful. Crosshatching...
And btw, it looks absolutely fabulous. (I'm loving Mikkel's hair)
I am going to comment on things now:
Haiz, I have great respect for pen-drawings. I'd just like you to know that.
Sigrid Marie, this is how I always see Sigrun
Piney, the red hair is a very lovely touch.