
Draw a picture!! This almost always helps.

Assign variables to all changing values. List everything you
know: Which variable do you know about? Which variable are you trying
to figure out?

Label your picture with variables and constants (to avoid confusion,
do not assign names to constant values).

Figure out how the variables are related, and write down an
equation. This is where you bring in knowledge from outside of
calculus, typically geometry or physics. If the variables represent
two sides of a right triangle, use the Pythagorean theorem. If the
variables represent the radius and volume of a sphere, use the formula
for volume in terms of radius. You don't have to express one of the
variables in terms of the other  just find an equation that involves
both.

If there are more than two variables, find a relationship to eliminate
one.

Differentiate your equation(s) with respect to time.

Solve for the rate of change of the variable you want in terms of the
rate of change of the variable you already understand.

If a variable assumes a specific value under some conditions (for example the velocity changes, but it equals 2 mph at 4 PM), replace it at this time. Remember to plugin after differentiating. (Why?)
Convert that information into an answer to your question.
