As teachers, we know problem solving to be where the rubber hits the road. Knowing how to problem solve and work word problems is where true understanding and application of math skills resides. It's the goal of all we teach in math.
Often instruction in attacking word problems become a list of "key words". But, key words can and will be used against your students as real math is much more complicated than that. I believe that key words are a crutch we offer students when they struggle, a quick fix. They are nice to know but not the road to true understanding and confident problem solving.
Here's an alternative. Teach students to be detectives and decipher each problem with code cracking skills. If students look at each word problem as a coded message that needs to cracked open, they are in a position of inquiry instead of answer finding. That is the right mindset for learning from and attacking problem solving.
What are the numbers?
What is the problem asking me to do? (combine, separate, compare- what kind of comparison?, group, cut, spread out over time, rational groups, fraction of a fraction, find how much you need of something...)
Addition: combining or finding a total
Subtraction: finding the difference between groups, finding how much more/less, finding how much further/less, figuring how much was taken away (eaten, spent...)
Multiplication: Finding part of a whole, finding the total rate, finding how much you need for a group of something or someone, find the total of equal groups
Division: dividing an amount into equal groups, using an equal amount of something over a time period, dividing an amount in to equal pieces, finding how many partial groups (fractional) you can make using a set amount
Use what you are being asked to do to choose a Strategy (how you are going to deal with the numbers): counting, skip counting, counting on, using friendly numbers (number bonds), splitting into place value, repeated addition/subtraction, use related facts, use the distributive property, equivalent ratios, use an algorithm...
Create a Model (show the relationships and make your strategy visible to others): diagram, picture, array, ten-frame, number line, counters...
What did you do to solve the problem?
Write down or tell the steps you took and explain what you were thinking as you choose those steps. HINT: Why that step, that strategy and that model and not something else?
It's a lot to remember. Grab the [FREE] Problem Solving Cheat Sheet here.