I’ve talked a few times about the importance of having a Customer Relationship Manager. This can be as simple as an excel spreadsheet. All you need is a record of who your client is, contact details, and as much info as possible about what you have done for them and where there may be more opportunities for work. You should always have a note of when you last contacted them and when you plan to again. Certainly twice a year should be a minimum until they say otherwise.
Having a regular emailer is always a useful way in which to keep in touch with people. It may be worth having a separate email specifically for existing clients. This email does not need to be as sales lead as your main one and can give more insights into behind the scenes.
Alongside this it’s always worth calling up a client. As above I would think a quick catch up is usually worth doing once every six months. I’ve done this for a number of clients over the years and its surprising how often a client has vanished purely because your old contact has moved on. Don’t underestimate the importance of keeping in touch with your clients as you are far more likely to get work from someone who has used you before.
One question I’m often posed is whether or not you should send your clients gifts/giveaways as a way of keeping your name in front of them. Generally I would suggest that gifts won’t have a big impact on decisions, and in fact many companies have a strict policy against them. I think your work should be enough on its own, but where you have a high value contract it might not hurt.
Always worth following your client’s on their various social media. Linkedin is obviously a great place for people to see your updates. It’s important though that you have a professional barrier in place. I wouldn’t add clients on facebook or anywhere you’re likely to share personal events, even if you might consider them as friends. A little bit of distance is advised.