Click the Cylindrical button. None of the automatic axis will actually line up with the arm's angle. Instead rotate and move the gizmo until it's about the correct angle and then click the Fit button and it'll hug the arm better. Check from multiple angles to see if you're getting the best angle on the arm.

Also remember to scale (make sure it's set to scale on Local Axis) so the checkers are closer to square.

When you've got the gizmo to the best size and shape you can, click the cylindrical button again to deactivate it and click the edit button to open the UV Edit window.

Just like with the pants, the edge that's in the center of the inner side is the one that we want the seam to fall on. Go to verticies selection and select any faces that are on on the wrong side of the seam that should be on the other side, Detach (Ctrl+D) and Move them to the other side.

Clean up any stretching or squished areas, and when you're done, freeform transform it into the square, render the UV texture out, Save it, close the edit window, and collapse the stack.

Onto the hands!
The hand will be much harder to unwrap then the previous objects we've done up to this point. It has a lot more little tweaking. Just use all of the knowledge that you've gained up to this point on the previous parts and do your best. And remember, it never hurts to just start over on the unwrapping. You learn from every mistake you make.

Here's basically what I did...

First I selected the body of the hand (both top and palm) and did a cylindrical map. Rotated, moved, and scaled the gizmo till it fit around the hand like in the image below.

Next I selected all the fingers and did a planar map on them all at once.

I Clicked the Edit button to open the edit winow. In the main viewport I selected the top of the hand and all the fingers like in the image below. The in the Edit UVs window, I Detached (Ctrl+d) the selected faces from the rest of the hand, flipped them horizontally, and moved them off to the side.

In verticies select mode, I moved and target welded the palm and top of hand so that they were connected along one side (the side opposit the thumb).

Then I did the same with the fingers, scaled the fingers down so they matched up with the palm of the hand and lined them up next to each other.

I moved, and target welded the verticies until I had the whole body of the hand and the fingers combined together in one unit.

For the thumb, I did two planar unwraps. It seems like a cylindrical map would work, but the thumb is just such an odd shape and curves in an odd fashion that it makes the cylindrical map more of a headache to deal with then just combining two planars.

Don't worry if edges don't line up very well, and don't be afraid to move things around a lot. They'll still look okay in the final texture as long as you keep the general size and shape os the faces close to their original unwrap.

Once I had both the hand and thumb unwrapped, I combined them together to reduce the number of seams. It's best if you can get the top of the thumb/hand combined together and leave the seam in the palm since it won't be as visable there.

Once I was finished, I used the freeform tool to scale the hand to fill the entire box. The hand is really stretched by doing this, but my intention is to have the hand be a rectangle rather then a square texture.

To do this, in the Render UVs window, I enter the dimentions 256x128, and when I click the Render UV Texture button, the map it generates is rectangular instead of the stretched square.

Hands are done! All that's left is the head.