1. Consistency.
Your postcards should have one goal, one objective, one service and one product. You should have a definite and clear understanding of what you want you message to convey even before starting having your own postcards. Having more than one of these is a sure way of reducing the impact of your message.
Keep in mind that your postcards can be understood at a glance. That your readers do not have to go through extreme measures to be able to know what is being said in your cards. Make sure you stop them instantly.

2. Significance.
Are you offering to the right audience? Are you certain that your readers are in need of the product or service your postcards are showing?
Even if you have the perfect postcards when the people receiving them are in no way interested in your offers, then all your efforts will just be wasted. It is important that you know what your audience wants and needs. After that, you can give out an offer they will not be able to refuse.
Make the most of direct mail marketing. You just have to know your audience, focus on them and give them what they want. Have one specific target customer. Then make your list grow from there. That is the way to do it.

3. Simplicity.
Ok, so you may have a lot of ideas you want to put all in your small card. And you have a great designer to make them all happen. Before you go on with your plans, make sure that you know the difference between a nice and an effective postcard. Being beautiful does not mean it will bring in the customers. Sometimes, it does the opposite.
Simplicity is a virtue. Everything and anything else has already been done. And audiences have seen them all too. If you want to be different, try having simple postcards. That would surely be a nice and soothing change from the usual.

Take these three factors into consideration and you will be on your way to stopping your customers in their tracks.