Recently, my best friend and her mom planned a surprise for my best friend. The toughest part about planning the surprise is keeping it from the person you tell everything to, and I mean everything. Even though withholding secrets from your best friend might sound sketchy, I promise you nine times out of 10 it is not.
1. Surprises.
If you are surprising your best friend, not ruining the surprise is your number one priority. By all means, do whatever it takes to not spill the beans. Lie if you have to. I would consider this to be the one exception to lying that is OK. Just don't make up an elaborate lie. Stick to simplicity; it's easier to remember.
2. If you know something that isn't worth sharing because it will only make your friend feel worse, don't share it.
Everyone at one point or another has a fight with their best friend. Make sure you live by the motherly motto, "If you have nothing nice to say, don't say anything at all." Sure, you can get mad at your best friend and they can get mad at you, too, but don't ever say anything extremely mean. Remember it's a bump in the road, not a dead end. You don't want that friendship to end.
3. Saying the wrong thing at the wrong time.
What I mean is saying something that could potentially get them in ton of trouble with their boss, parents, siblings, other friends or significant other. There is a time and place for certain conversations; make sure you know the appropriate time. This doesn't mean to not embarrass them; by all means embarrass them. Everyone knows I embarrass my best friend frequently.