You use Meteor.callSync and Meteor.applySync exactly as their counterparts, Meteor.call and Meteor.apply.
Note - this package requires using the 1.2-rc.16 Meteor release.
This package makes use of two undocumented options for calling Meteor Methods. The first is the returnStubValue which will cause the return value from a Meteor method stub to actually be returned instead of undefined. The second is the recently created throwStubExceptions option. With this option, Meteor method stubs will throw exceptions instead of logging them to the console. If an exception is thrown, the method will not be run on the server. Meteor.callSync and Meteor.applySync sets these options to true so you don't have to remember to.