What's your best social media marketing tip?

I would say there is no such strategy is best. It depends upon insights and direction of marketing campaign. One may choose different strategies focusing different aspects of social media marketing. 

But there are some  suggestions:

- create your campaign with good content

- market your product with the target social groups and communities in social media platform (age, sex etc)

- Create a event, where participants can win prizes for sharing

and like.

Choose right platform for boosting your services and build online relationship with your fans.

Use colorful images and concepts to improve engagements especially with tweets and re-efforts.

It is different for different social media platforms based on their functionality. In Facebook, you can do marketing through facebook page and advertising (text, display or pop-up) etc...

competition between my marketing and other virtual marketing I create

By asking yourself how to do it better.

Test your copies, images, colors, fonts, targets and use data to make decision.

marketing through the advertising

Use Graphics as much as possible and jump into groups

Use crossmedia (for example, the good image and client targeted advices in forums + social networks) !!!

...But dont forget to reach people by CEO...

Media + covering gives mist effective adv campaign