Sometimes when I find myself in a rut and I need to get some ideas to get the ball rolling on my campaigns I look to videos and articles to get those ideas. The above video has 4 employees of Wizards of the Coast (WoTC) answering some questions in a panel format. They answer questions from what a DM needs to do to be a better DM to how to get a split party back to the same plot thread.
If this kind of open panel isn't something you think you'd enjoy, I'd say give it a shot, and if it still isn't sufficient, perhaps try listening to some campaign podcasts (whether they run the same edition as you or not) to try and find aspects that you like from the DM, or from the campaign, to spur your creative thinking into your own campaign.