In addition to what's been said:
Front wheel has three different types of spokes.
1. Nine brake side inner.
2. Nine brake side outer (these have more of a fish-hook bend than the inners).
3. Eighteen non-brake side inner (be worth double checking that they are all the same length, and not 9 that are slightly longer than the other 9).
I think the same is true for the rear on an IT175H.
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Most dirt bike wheels are "two cross", meaning that each spoke crosses two other spokes between the hub and the rim - noromally one just out of the hub and the other about halfway along. You can see this in Colj's photo.
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The biggest/most helpful thing to get your head around, is to realise that every 4th spoke (at the rim) comes from the same spot on the hub.
Every 2nd spoke (at the rim) comes from the same side of the hub.
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Used hubs will have witness marks from the old spokes. This makes life a lot easier because it clearly shows which direction the spoke should be going.
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Tensioning and truing is the real challenge, especially if you are using old rims that aren't dead straight... That'll be another post.