Q: We have a few under-performing products and some that are breaking sales records. Should our marketing efforts focus on selling more of the under-performers or driving more sales to the top products?
A: I'd focus on the top product line and do some market research on why the under-performing products aren't doing as well. In addition to finding out why customers aren't responding to the under-performing products, try asking them what they like about the top products.
Also remember that some products have shorter life cycles than others. For that reason, it's always good to have new products in the development stage. Your under-performing products may be nearing the end of their life cycles, in which case, you may want to consider rejuvenating them by adding new features and finding new uses for them. A great resource on product life cycles can be found online here.
It might be wise to use some of the resources from the high-sales product line to create new products that could potentially have a similar payoff. That way, you won't run the risk of overselling your top performers by investing in more marketing when you haven't prepared for the road ahead.