Before a campaign starts, it is vital to get a read on your players. You must figure out what your players like and then make sure your game works for them. If everybody wants to play a sandbox game, then you are either going to run a sandbox game or your campaign is going to fall apart.
One way to get a read on your players is to give them a short survey. It may sound a little corny, but it's far better to know what they want now then to be surprised with it later. The survey should tell you everything you need to know about designing and running your campaign. Remember - if your players don't have a good time, the campaign will fall apart!
Once you have responses from all of your players, then you can start to analyze. Try to built your campaign right about at the average of what people want. For example, if most people want a sandbox campaign, then you should try to either run a sandbox campaign, or adapt your current plan to be more sandboxy.
Some questions you should consider on a player by player basis. For example, some players will be comfortable with character death, and some of them will not. Try to avoid killing the characters who don't want to die, and not pull any punches with the players who don't mind.
You can find the New Campaign Questionnaire at this link. Simply open the spreadsheet, copy it to your google drive and then send it out to your players!
Take a look at the New Campaign Questionnaire Here!