How do I become?
I understand I have to do 3 things for the townsfolk:
First I have done Vaermina's quest "Walking Nightmare",
I have killed a dragon which the Jarl put a bounty out for,
i have killed a Troll he asked to do,
And finally I read on UESP that if you sell ore that counts as well.

BUT my journal is telling me I have only completed 1/3.

Help?

Did you do those things before he asked ou to do 3 things? It only counts after he asks you, go to tavern and talk to everyone, they will give you little tasks like get them a drink.

Kiliing the troll or the dragon: doesn't count.

If you don't mind spoilers, here are the quests you can do to become Thane:

http://elderscrolls.wikia.com/wiki/Becoming_Thane

Excellent, thank you.