What have you learnt in the course of your career that would be really useful for colleagues here on the Learning and Skills Group to know about? It could be totally tactical ('Always begin a public presentation with a full set of lungs') or utterly strategic ("Never begin an L&D plan without first knowing which executive gives you complete support.")
The only thing it has to be is short.
To start off, here's my offering: Never say 'yes' to a training request without first asking 'why?'.
Don't jump at new technology just because it is the latest fad. Make sure you understand what it can do, what value it will add to your organisation, and whether your users actually want / need it.
Slightly bending the rules by offering ten tips instead of one, but my top instructional design tips echo some of what's here, along with some other ideas.
"Put yourself in their place / Understand your audience"
Of course you'll understand everything you're trying to deliver (no matter what the medium of delivery is) - however if it isn't clear, consise and easily comprehendable - the "learner" won't understand. And if you can "relate" to their scenarios/position - it's easier for them to understand and far more believable!
An essential question to ask following any learning intervention is "what are you doing differently / better as a result of the training?" After a while it becomes a habit to ask it. Even better, when people see you coming they know you're going to ask it....and after a while it becomes a habit that they think about the question even before you ask!
My top tip is to never allow the commissioner of the training to think that a single training event can fix the issues without followup and further support. In this respect I agree with Sumeet.
My top tip is... Learn from your successes. Quite right to focus on things that didn't go well but understanding why things went well too is equally relevant.
Walk the talk: be an active learner in ways that excite you and you want to share with others. If we in L&D aren't enthusiastic and engaged learners, how can we expect others to be?