Sharing three tips that I practice (I wasn't aware at first, then I noticed that magic happens when I do these 3 things) that make my clients stay. I operate a B2B business, so majority of my examples apply to B2B.
1. Impart Value. This is a marketing must-have in today's fast paced, too-many-options world. Value can mean giving free content or resources, online or offline. It can also mean going the extra mile for your clients, delivering not only what is expected, but exceeding that. Value is also not always charging for every little request. For me, if it will take you only a few minutes to do it, not affecting any other major tasks you have, then you can do it for free as an extra service for your client. They would highly appreciate that.
2. Invest on Them. It's our customers who should be spending money on us, right? Yes. BUT we should also be spending money on them. It's not a one way deal. Investing on our clients can mean buying snacks for them during meetings, giving them little souvenirs when we go out of town, or being their customer as well. Whatever they're selling, buy one for yourself. Use it and appreciate it. Knowing your client's product will also help you in serving them better.
In a B2C setup, you can sacrifice some profit by giving them rebates, discounts, or freebies. You can also organize free events that they will enjoy, or give them VIP treatments whenever possible.
3. Be Involved. Be like family to them. Talk about other things aside from work. Ask how their family is doing, or how their vacation went. Greet them during special occasions. Talk about the latest car, restaurant, or whatever sparks interest. Before you know it, you will be real friends with them and that is good for business.
For B2C, getting involved with your customers can mean having a good CRM system. Knowing their frequent orders, birthdays, civil status, address, email and mobile # can do wonders. You can text or email (or automate this) them when it's their usual time of order, or greet them when it's their birthday, or email them new products and promos that they might be interested in based on their buying behavior. Big online shops do this, and it does wonders for them.