There have been some great posts already.

In my opinion, the actual defensive movement you make is the last important part. It starts with range. The right hand is a punch that really requires the guy hitting you to establish his distance before throwing it. It's very difficult to throw a right hand while advancing without compromising stance, balance and head placement. Most times guys will end up squaring their stance and leaning forward, in prime position to be knocked on their ass. You have already been given tips on how to fix your stance so that the right hand naturally has a farther distance to travel. With your head offline to the right, your head is both across their body and farther back. If they try to just throw it, you'll see it coming so far away that you'll have time to ask your coach what counter he wants to see. When your upper body is more square, your head is closer and with your glove in place it is harder for you to see that right hand coming.

With your stance better suited to defending, make sure you don't let your opponent establish their range. Your jab will be critical for this. If they feel like they can walk into your space whenever they want, you can bet that right hook will be coming your way. Lucky for you, jabbing from the stance that has been suggested to you will discourage them. I especially like jabbing from a slightly lower lead hand position. It becomes very hard to see and gives it enough stopping power that no one is gonna walk through it if you hold your ground when you throw it. This will take away their ability to throw it until they can get their feet set in your range. An active, threatening lead hand has been the greatest tool to decrease the amount of right hands I get hit with once I was instructed on the importance of range, and when I get hit by these punches it's against guys who can take away my jab and force the range they want.

If your stance is good and your jab is preventing them from getting into position easily, you should be able to worry less about that punch.

As for specifically defending it, jabbing from a good position will leave you ready to easily defend a right hook. If you jab and he throws it, just bend your knees and keep your weight on your right foot while keeping your jabbing arm in place. Either the arm or shoulder will deflect the punch, and you can come back with your uppercut. The same counter works if you aren't jabbing too, Mike McCallum was very good at doing it to the head and body as was James Toney I believe. You can also fade the punch by pivoting clockwise (range is critical, you need to pivot PAST it not INTO it) then fire back your own right hand or step in with your 1-2 if you end up too far away. This isn't my personal favorite, but it's also possible to roll under it and come back up on the either side, hitting him with your left to the body. These are all responses you can drill, but limiting the opponent's opportunity to throw them will get the most return on your investment until you can figure out how to make him throw them when you want him to.