You don't have to know all there is to know about a particular task, that's why you outsource to the pros.

However I wouldn't take on a project unless I have some knowledge and understanding of what's being requested.

That's why it's important to know the strenghs and weakness of your team and also to build relationships and contacts with different vendors, you'll never know when someone else's skills will make you money.

Also, always underpromise and overdeliver.

I see people giving this advice all the time... I think
they couldn't be more wrong. If you don't know how
to do something yourself tell me how you'll know if the
outsourced sub-contractor knows what they're doing?

Outsourcing isn't for those who don't know what they're
doing... it's for those who know what they're doing but can
be more productive and profitable focusing on other aspects
of their business. You don't have to be an expert at every
phase of a project but you better know what is required for
it to be done correctly.

If the project crashes and burns because a sub-contractor screws
up you'll still be the one to face the fire. You're personal reputation
is on the line no matter who actually does the work.

Better know what you're doing....

Looks like Adrian and I had pretty mush the same thoughts at the same time... lol

One of the best ways I've found to not get caught in this crux is to firmly tell clients "when they sign up" exactly what areas you specialize in and that anything outside that as a request can be addressed but it doesn't promise we'll accept doing it.

If its something better suited to a more focused skill I'll be happy help you in any way I can.

You have to remain focused on your core services until you can learn other things. Until then you aren't everything to everybody and trying to be is a great way to get off the derailed.