Lets say we subscribe like this

const sub = Meteor.subscribe('sub');

then we check if the sub is ready

const localCollection = new Mongo.Collection(null);
if (sub.ready()) {
  // then we dump into a local collection
  localCollection.insert(Example.find().fetch());
}

now we can interface our state on the client purely through this local collection and updates to it do not sync to the server until you handle this manually.