Something I've often told students is, "Clean the kitchen before you start cooking" (or, "Clean the workshop before you start building"). What I mean is, when you have a complicated equation, simplify each side, before you start moving things around on both sides. It's much easier to keep track of things when there isn't a mess lying around on the counter.
On the other hand, there are times when multiplying both sides by a denominator to eliminate a fraction is safer, because the work with fractions in simplifying would be too error-prone. You have to decide what's best for you. This example is dangerous no matter what you do first!