What is the biggest marketing mistake you see photographers often making?
Hands down, giving away the high resolution files or selling them for a very low price. If you give away the files for $1000, you will never have a sale over $1000. Price the files according to your sales goal or sell them at $x after a $x sale. Those files have huge value… they are everything. If you are pricing them under $500-1000 and have any sort of legitimate business expenses, I promise you are losing money. (My high resolution negatives are $5500 or $3500 after a $5000 sale, which truly plants the seed that these are the ultimate collection and have a real value.) If you want to work for charity, find a non-profit that is helping the needy.