Excel is a widely used tool – many resources are available when you have an issue
Within Excel
Prompts to remind you what functions do and what you need to input
Suggests solutions to error messages
Excel Help online
Great resource which details all functions
For each function, details each argument in a step by step way
Google!
Most mistakes you make have been made hundreds of times before
Using a simple Google search will often direct you to the official Microsoft Office resource, or will lead you to advice from other Excel users like yourself
Your colleagues
There are tons of resources available, make sure you use them!
Qs: Anything else you use when you have trouble with excel?