First of all, will it make much difference which agency you choose?
Yes, Google AdWords is very analytical and also involves a lot marketing psychology. It is also very competitive as you appear alongside a lot of similar businesses that are competing for the same market. From personal experience I can tell you that a good agency can get you up to 4x more work for the same marketing budget, compared to a bad agency or someone trying to do it themselves. In some cases even more.
It is hard to tell if an adwords agency is going to get you the best return for your marketing investment. Here are some things you can ask about to help you decide.
Question 1) What reporting do they provide?
If they don’t report back on the actual number of enquiries you got (for service businesses) or total sales revenue (for ecommerce) then avoid them like the plague.
If they are only reporting back on statistics that are pretty meaningless to your business like the number of advert impressions and clicks then they probably aren’t tracking actual enquiries or sales revenue. It is impossible to create an effective campaign if you aren’t tracking the volume of enquiries / sales and most importantly where they are coming from.
Good tracking will reveal all sorts of insights on what is leading to enquiries like which keywords, time of day, device (mobile / desktop) and much more. Google even allows you to adjust targeting based on the user’s age and gender. All this can then be used to make the campaign use it’s spend more efficiently.
If you offer a service then most of your enquiries will probably come in via telephone. For this a good agency will probably recommend using third party call tracking software.
Question 2) What Do They Charge?
The fees should be in proportion to your spend. If you only plan to spend £100 per month on AdWords then even a good agency that charges £500 per month won’t lead to a good return, compared to an okay agency that will manage the campaign for £100 per month. Ideally you want an estimate of how much time they will spend on your campaign in exchange for the money.
Question 3) What Case Studies or Examples Of Success Do They Have?
Best case scenario is that they are already running a successful campaign(s) for a competitor and they have improved that over a number of years. Assuming the competitor is in a different geographic location or there isn’t some other conflict of interest if the agency acts for both of you.
Or they may have good campaigns for other similar industries like other tradesmen if that’s you, or other clothing retailers or whatever.
They should at least have other successful service based campaigns if you offer a service, or ecommerce, or Saas, or so on.
If they have similar clients that they have run successful campaigns for and there is no conflict of interest then there will be things the agency has learnt that they can reuse. The more similar the client the more likely they will be able to get your campaigns to perform. Running campaigns for 2 or more businesses in the same industry means the agency will have access to even more data and testing so both clients would benefit.
They should be able to give you an idea of what cost per enquiry and volume of enquiries they achieved or the return on ad spend for ecommerce.
Finding answers to those three questions for a few different agencies should help you make a better decision. If you are looking for an agency, feel free to ask me those three questions.