To that end, lets consider five ways you can easily add value to your consulting engagement that your client can see and keep with them to remind them of your top performance and value to the organization.
Conduct weekly touch base meetings and regular emails. Clients like to be updated. Staying too far away or too long out of touch may make you über productive but will also make the client über concerned. Or at some point it just might hit them in the middle of a meeting or when asked to get a referral for a good PM service that they haven't heard from you lately and they start to get sweaty. Avoid that paranoia from the customer. It's difficult sometimes to reset it. Keep them in the loop. Have a regular weekly meeting with them and some sort of daily communication (if it makes sense). Send out daily updates to the customer and all stakeholders. Make it like a project newsletter of you want, but make it quick and easy for you to provide yet informative enough to make the daily effort worth it.
Setup their social media presence for free. Go the extra mile. Yes, some of your clients don't have Twitter accounts, a LinkedIn presence or a Facebook page. Do it for them. Create what they are missing, promote it, and post content to it. It only takes you a few minutes to get them started but may mean the world to them. And you never have to tell them how easy it was.
Tweet regularly during the engagement about the company, products, and customer service. Sing their praises to the world - especially your own followers. Potentially, some of those followers could become your client's newest visitors and possibly customers. Great add-on benefit for exposure and hopefully sales.
Provide some short training for client staff. At some point, you'll be gone. You can include in your price some detailed training if, for example, you're setting up a small project management staff or office (PMO). But you could also provide some good mentoring to those who may be taking up the mantle you leave behind. Providing some hands on tool training and "real PM" strategies based on your own experiences and the need of their organization, industry and types of projects they are going to be leading would be extremely beneficial to your customer. You could also be part of the interviewing and hiring process for the staff that will be brought in permanently after your consulting engagement ends. I've done this on at least three engagements and it resulted in additional future work for me with all three of those clients.
Lead short weekly meetings to identify / discuss other organizational needs. You are there anyway and if they needed you for your current engagement then there are probably other areas of need you can help them identify - possibly even areas you can fill the void on since you're a jack of all trades, right? Conduct a 30 minute meeting once a week with your main sponsor or the CEO and select staff you are working with to give them an update on latest progress. Follow that with a 15-30 minute add-on session to talk about any other needs or areas of concern. Offer tips or suggestions on how to resolve or workaround issues they bring up. If the need is too large for that, then make a proposal and present it to your main contact or sponsor outside of that meeting.
The concept here is to leave the client environment a better and more productive place than it was when you arrived. That's what makes them call you back next time. And if some of that is tied into value added services that they paid little to no money for, then that is going to make a huge impression on that client. This is just a list of five – but continually look for ways to add benefit for not much effort and you'll likely find this client seeking you out more than just this once.