Well, that's a tough one. I'd start with four kinds of moves:

• something that happens immediately
• something that grants some kind of HOLD
• something where you get +1/-1 to your roll under circumstances
• something reversed, where a high param would be a bad thing

First category is straight forward:

• 10+ gives you what you'd expect from a success
• 7-9 is 'a worse outcome, hard bargain, or ugly choice'
• 6- give them hell :)

So the only tricky part is 7-9, let me try to give an example:

Let's say there is a drinking contest in the local inn and you want to participate (roll +CON): 10- you win, 6 - you get drunk, throw up all over the place and pass out/get sick debility/other bad things.

7-9 might be:

• a worse outcome (you wanted A, but you'll get only half of it)

  you end up close second and earn respect of the bartender and some locals (+1 to parley with them or they give you a quest)

• hard bargain (you wanted A and B, but you have to choose one)

  you and this other guy are the last ones in the game, you can either win it, but end up with a sick debility, or stop now to get second place and at least not pay for all the shots you've consumed

• ugly choice (you wanted A and B, but you're given a choice between C and D both of which is not what you wanted)

  you feel sick and get sick debility, or you fail spectacularly and let slip a fact you really shouldn’t have.

An advice on that: if you give your player a choice between several outcomes, makes sure they are equal, and there is no situation where every sane person would choose the same one. For instance:

You start to feel sick from all the drinks you've just consumed, choose one:

- you don't get sick debility
- you get to talk the bartender into not charging you for all the drinks
- you don't pass out and get all your items stolen

In the example above everyone would choose to keep their precious items, so you don't really give them any choice. To fix it either remove that option, or let them choose two (hopefully the other two would make it worth loosing all the items)

Moves that give you HOLD:

• 10+ get 3 HOLD
• 7-9 get 2 HOLD
• 6- get 1 HOLD in addition to what GM says

The tricky part is what you can spend your HOLD on. Make sure you can spend HOLD only on something that makes sense based on how you got HOLD, make sure all the options are equal, keep in mind that you move can be used by players of level 1 and level 10, so make it scalable.

Something like:

When you drink human blood roll + CON and get 1-2-3 HOLD; you can spend HOLD to:

- turn into a bat
- get +1d4 forward to your damage
- neglect all damage from a single blow

Next category would be roll w/o your params, but with +1/-1 from other circumstances:

When you search through Duke's library to get knowledge on a specific topic,
tell the GM what question you need to get an answer on, roll 2d6 and add:

+1 if you just need a yes/no answer
+1 if duke's librarian helps you
-1 if you do it under full moon

On 10+ you get the answer, on 7-9 you get a hint, GM will describe it.

And the last category would be a custom move, where high param is a bad thing. Something like:

The castle is too grim and depressive to be in, when you feel melancholic, roll+INT:

6- you're fine
7-9 choose one:
    - you get +1 DEPRESSION
    - you try to cut your veins - take 1d6 damage, ignoring armor
10+ you get +2 DEPRESSION

When your total DEPRESSION exceeds 10 you commit suicide

I hope all this will give you some ideas and inspirations.