Replicating schema changes between production and development databases
If you have access to a db version control system (ala Red Gate), you can have it create a deployment script fairly easily. 
If not, just create a file and script any ddl changes you make and store them in a file, then when you are ready (and have backed up prod) you can run the script against prod to make your changes. 
Be aware that certain changes can require extra steps (adding a not null column without a default is always a favorite), but that is the basic procedure. Also be aware of how your data might affect your ability to promote changes (key constraints, etc.) which is why tools like Red Gate's SQL Compare and Version control are worth the money.
No I don't work for Red Gate, but I've had to do this job with and without their tools and it is a lot more work without them.