You can always subscribe to one of the numerous database services that include information, and sometimes rankings, on Investment Advisors. These services tend to be fairly pricey, though, so they may not be your best choice. Another option is to find articles (yes, like this one) or free newsletters written by Investment Advisors. If you find one or several that make sense to you, check out the IA and see if there's chemistry between you.
If you believe markets are generally efficient and prefer to invest in an index mutual fund to achieve an index-like return, shopping for the best index mutual fund based on low fees and a low expense ratio makes good sense. The portfolio manager of an index mutual fund endeavors to invest the fund's assets to track the index as closely and cost-effectively as possible. Larger index funds have an advantage in that they can spread their operating costs over a larger asset base.
Contributing regularly makes investing easier and puts your money to work sooner. Through a continuous purchase plan, like those available from BMO Mutual Funds, you will be contributing more regularly such as monthly or bi-weekly. This gives you the comfort and convenience of making smaller, regular contributions to your RSP portfolio and it means your retirement account can grow considerably, due to the remarkable impact of compounding.