I'm going to leave out what everyone knows,stuff like content is king,participation in stumbleupon
Short posts
Stumblers skip stuff if they feel it will take too much of their time.So edit like crazy and write as if each word costs a million
Picturify
Use lots of images.Adding images grabs attention.It gives the impression that you have put in a lot of work.Stumblers cant resist to give a thumbs up if they feel you have put in work.
Divide and conquer
Always divide your posts into sub sections.Stumblers like to read only what they want,it will also make the posts easier to understand.
Add bookmark buttons
Add bookmark buttons and make them easily noticeable.It will remind your visitors to stumble your posts.
Stumble exchange
You can get others to stumble you posts in exchange for your stumbles or something else in kind.Entrecard forums is a great place for this.
Stumbleudon
Stumbleudon is a service which uses your account to stumble someone else's page while using their account to stumble yours.It may help.I personally dont use this.I feel that it can also get you banned sometimes.