What are some best practices for compensating sales-related positions such as Account Managers, Bus Dev Managers, and Tech Sales Support Specialists?

You are asking a question that has challenged many companies and over the 12 years I've been in the field I've seen this pendulum swing all the way to one side and back again. As I often tell clients, "the great thing about incentives is they work, the bad thing about incentives is they work" and often they work so well for one set of positions that the company decides if it is good for the sales force it must be good for the whole company, and before you know it administrative assistants are being paid based on number of emails answered. Banking went through this trend several years ago (you may remember being "sold to" by your teller when you were just trying to make a deposit). There was a time when banks considered just about every employee a sales person and had them all on some type of sales incentive plan.

The roles you ask about (account manager, business development manager, technical sales support specialists, and sales engineers) are more in the gray area in terms of eligibility for "sales-type" incentive plans. I would need to know more about the exact job descriptions before I could give an opinion about whether or not the role should be on a sales incentive plan or a corporate-wide plan based on overall company performance as Account Manager (which is a very common selling role title with best-practices all its own in terms of incentive design) may not mean to your company what it means in other companies.

That being said, here is some general guidance that may be of help. If performance in the role is OBJECTIVELY MEASUREABLE on an individual basis and the result of that performance has SIGNIFICANT BUSINESS IMPACT then you should seriously consider investing the time and expense in developing a customized incentive program. If you can't objectively measure individual (or small team) performance and/or the performance impact has limited business impact, then you are better off leaving them on the corporate-wide plan. Developing sales-type incentive plans (often referred to as customized plans for non-selling roles), takes significant time and effort and can be complicated to track and administer. You have to be sure that the resulting change in behavior that you may get from the plan is worth the added administrative expense.

If your Account Managers are individually responsible to manage and grow a defined set of accounts, with objectives such as upselling, retention, penetration, and growth of those accounts then this role should be on a sales incentive plan (but the plan would look very different than plan for a sale reps plan who is out selling widgets every day, and might not use a commission structure at all, but instead use a goal-based bonus approach).
Business Development Managers could be low level lead generators, or could be out closing really large new business deals on their own. My hunch is that it is likely this role would be on a sales incentive plan, but the exact nature would depend on the accountabilities and expectations of the role.

Technical Sales Support Specialists (if this role is similar to what I've seen elsewhere) are often paid using a less variable pay mix (80/20 or 85/15) and are paid based on the results of the sales reps they support. This is also the case for Sales Engineers, although these roles often support the entire sales organization w/o being directly aligned to a team of reps, so their individual contribution becomes even less clear. For these two roles, the line starts to blur between corporate plan and sales plan, and often you end up with a hybrid. Part of their plan is like the corporate plan, but there may be a portion that is tied to the overall performance of the sales team as a whole or the sales region or team they support. There can also be a small individual performance modifier, but this often based on subjective manager evaluation.