Risetime is typically measured as the time delay for a signal to move from 10% of max amplitude to 90% of max amplitude. In some cases, a 20%/80% measurement will be made also. Many modern scopes can provide accurate risetime measurements of signals.

Overshoot is the additional "ringing" at the top of the pulse before the signal settles in at the top amplitude. Overshoot is typically problematic and manufacturers take great care to minimize overshoot.

To maintain the highest possible rise time, care must be taken with cabling and termination. Low capacitance cable and 50 ohm termination will provide the fastest rise times without overshoot. Faster rise times can be achieved by increasing the termination resistance, but some overshoot is likely to occur.

Overshoot is often related to voltage as well. Here is once example: