If you want qualified leads think "subscriber lists." These can be your own subscriber lists if you publish your own newsletter or if you teach an email workshop, or you can purchase the suscriber lists of other companies.
To find these "subscriber lists" put "subscriber lists" in your search engine.
You can purchase subscriber lists from Business.com and BestPricedLists.com for example. Best Priced Lists provides you with a free quote.
You can get free quotes from list vendors at QuoteAList.com.
At Zeop.com you can build your own email subscription list free. You get a free email subscriber form for you website.
Seeking wealthy investors for your subscriber lists, then go to RichList.com.
Want guaranteed lists go to GuaranteedLists.com.
Subscribers lists are also available from GreatLists.com.
The best way to get your own qualified leads, of course, is to have your own ezine and your own subscribers. The ezine itself can be a freebie and/or you can offer freebies in your ezine to attract new subscribers.
When you have a subscribers list, your ads, then become targetted ads to customers and potential customers who you know are interested in your products and services.
What information should you request on your subscribers form. You can request only name and email and/or you can request address and telephone number. This subscribing then also become a mailing list and targeted telemarketing list. However, you should ask clients permission before telemarketing.