If you want to keep it friendly, you're probably better off talking to them in person - if you put it in writing, it seems a lot more formal. Personally, I'd try talking to your neighbor face-to-face before putting pen to paper!
What Should I Say To My Neighbor?
Tell them the truth, but avoid confrontation if you can. Just explain that their dog is keeping you awake or preventing you from working, and that you'd really appreciate it if they could do something about it - for example, keep the dog indoors at night, or train it, or calm it down in some way.
Don't feel embarrassed to say something - you're well within your rights, as barking does count as noise pollution, and your neighbors are being inconsiderate.
What Should I Do If That Doesn't Work?
If saying something to your neighbor doesn't get you anywhere, I'd then suggest writing them a letter. This is more formal than talking to them, and so it's more likely to get results, but probably won't improve your relationship!
You may want to explain in the letter that if the barking carries on, you'll call or write to the local council (or whoever deals with this sort of thing where you live) and let them take action.
Good luck!
Don't feel embarrassed to say something - you're well within your rights, as barking does count as noise pollution, and your neighbors are being inconsiderate.
What Should I Do If That Doesn't Work?
If saying something to your neighbor doesn't get you anywhere, I'd then suggest writing them a letter. This is more formal than talking to them, and so it's more likely to get results, but probably won't improve your relationship!
You may want to explain in the letter that if the barking carries on, you'll call or write to the local council (or whoever deals with this sort of thing where you live) and let them take action.
Good luck!