Here are few tips on how to proceed in solving problems in Physics 101
1. Read the problem carefully.
2. Draw a diagram. A picture, even if it is so simple-minded as to seem silly, is worth hundred lines of algebra.
3. List all quantities given and requested.
4. Try to understand the behavior of the system qualitatively. Play with the situation either mentally or using physical models. Look for simpler special cases (a right angle, an infinite mass, a zero length, etc.) where the solution to the problem is more transparent.
5. Determine the problem type (response to a force, energy conservation, equilibrium, etc.) and write down principles and equations which apply to this kind of problem. Write down too many. It is easier to ignore excess information than to realize something needed is missing. Add to the list of quantities made in step 3 any that are normally needed for this type of problem which are not specifically mentioned in the problem statement.
6. Work on the algebra to reduce the number of unknowns. In general, having the same number of relevant, independent equations as unknowns means there are enough equations. If necessary, add to the list of quantities made in step 3 any additional quantities which can be calculated using the equations from step 5. Finally, check for relations that may have been overlooked in step 5.
7. Calculate the algebraic solution.
8. If a numerical solution is requested, put in numbers with units. Make sure all the numbers you use are in the same set of units.
Plausibility (Is the algebra OK? Are the numbers reasonable?)
Units (Are all units consistent and appropriate?)
Notation (Are vector quantities labeled as such?)
Special cases (Is the solution consistent with the special cases of step 4?)