One of the key advantages of promotional products as an advertising medium is their ability to target an intended audience.  Whether that target is media buyers, mothers, engineers, college students, your employees- or whomever you’re trying to reach - there is a promotional product that will appeal to that group of people.  
One of the first questions I will ask clients when discussing a project is ‘who are you trying to reach’ with the item(s) that you’re looking to order?  Once I understand the target, I can then start thinking about which items might be able to gain their attention .
What’s really nice about promotional products is that there are so many different items  available at all kinds of price points.  The real key to making them work is marrying the intended audience with the marketing message and of course, the available budget.
So for example if your intended target is real estate agents, I’ll start to think about which types of products they might find useful at a time when they’ll be receptive to the intended message.  Agents typically spend lots of time in cars - so something that goes in the car when they’re driving to a property might be one way to go.  Or maybe they’ll be more likely to think about your product/service/message while they’re at a desk doing online research or calling on their phone.
The really cool thing about promotional products is there are items for each of these situations!
Then consider that those items will engage their recipients in a manner that’s unlike any other advertising medium.  Nothing targets an audience quite as effectively as promotional products!