I always tip more than 15% or 18% but don't go crazy. I usually stick to close to 20%. MSCs won't cover the extra little bit I throw in, but I don't see that as a problem at all. Well, after many, many years with a particular MSC, I received a note from an editor stating that I tipped too much and that while the extra wouldn't be reimbursed, doing so would make me stand out. I highly doubt $8 to $10 on a $40ish check made me stand out. My husband said to just go back to tipping what the percentage stated in the guidelines. I don't want to cause trouble, but you would think after maybe 7 or 8 years with this particular MSC, someone would have called me out before now. The amount the editor is upset over is maybe $2. Just wanted to start a conversation about this topic - do you "over tip" when the guidelines say they will only cover a certain amount? Leave some on the card and some in cash (I think that makes you stand out more!)? Only tip 15% wherever you go and go up to 18% or 20% when its required by the guidelines? Been called out for this "grand gesture?"
Doing what I can to enhance the life of my family! I LOVE what I do 
