For outdoor use, I recommend using Douglas fir or vertical grain Douglas fir. These woods hold up very well in outdoor conditions over time. For indoor signs, good choices are...
Most of these pointers would make any teacher happy, but there are always a few bad apples out there. In those rare cases, no matter how hard you try to...
Any interior paint will do. The higher quality of paint you use, the longer it should last. If you're going a lighter color, make sure you use primer first.