I feel that I understand the strategy and tactics of online marketing fairly well. However, I need help with offline marketing. What offline marketing strategies worked well for you? It seems to me that offline marketing such as sending letters to a list costs a lot and produce very little respone. Any tips or pointers wil be appreciated.

You asked a question I struggled with a few years back.  Here are my thoughts from what I've done to address it over the past few years...

In my experience, people are simply looking for proof that their vendor (salesperson, contact, provider...) is an expert in whatever they proffer.  Sending unsolicited letters doesn't necessarily help you rise above the fray (although it's a little better than dreaded - and utterly embarrassing - cold calls)....Really, I think it's better ONLY because the salesperson doesn't get hung up on - they get tossed in the trash, instead.  At least they're not there for it...

Regardless, I think you can be seen as an expert in a number of ways.  Put yourself in the mind of your prospect.  What evidence would she need to view you as an expert?  Perhaps if you delivered a speech addressing the problem she needs fixed?  Maybe if she reads an article you authored that links her problem to your solution?  The one that's been the best for me?  When a client recommends ME to one of their friends...You have to have the nerve to ASK FOR REFERRALS, THOUGH.  For more on that, check out Bill Cates.  He comes at it from a financial planner's background, but he's the best there is on the topic.

A takeoff on the referral concept is to get "endorsements."  Consider candidates for political office.  They clamber for the support of organizations that represent others (Associations, Unions, etc.)  What's to prevent a salesperson from seeking the same thing?  Why not work to get the support - endorsement - of the Association(s) your prospects are a part of?  It may be tough, but would probably be worth the effort...

One of the most successful offline marketing efforts I've ever been involved with went like this:  I was working for a high-tech consulting company selling to (somewhat) low-tech clients.  We put together a high-end wedding-like invitation to a seminar that we delivered.  The topic was innocuous (we didn't hide what we were about or who we were), but clearly addressed a problem our prospects faced.  Was it expensive?  Yes.  Was it worth it?  Absolutely.  Granted, we were selling in our local area (is that something you're doing, as well?) 

Sorry to drone on, but you really hit a topic I've thought a lot about.  I'd love to hear your thoughts...tell me if I'm off-base.