If you collect Magician autographs, there are several "tricks" to help you get the most from eBay.  I've been collecting magic autographs more than thirty years.  It's a fun hobby, because Magicians are interesting characters and Magic is a unique performing art. 

There is an amazing quantity of Magic autographs available every week on eBay: some great bargains, and some not-so-greats.  Here's my advice for buyers of Magician autographs.

First, identify your collecting goal.  A collection is more interesting if it has a focus.  Are you trying to collect everything there is on David Copperfield?  Do you crave signed Magician posters?  How about autographed playing cards?  Here's some examples of Magic autograph collections:

1. Specific Magicians, like Mark Wilson, Copperfield, Houdini, Siegfried & Roy, Penn & Teller, Andre Kole, Criss Angel or David Blaine
2. Specific objects, like signed photos, posters, tickets, letters, playing cards, books or lecture notes
3. Categories of Magicians, like escape artists, mentalists, sleight-of-hand artists or illusionists

Second, research the market on Magician's autographs, to see who's available and how much they cost.  Periodically check "Completed Listings" too, to see what things really sold for.  Some magic autographs are hard to find, others are more plentiful.  Living Magicians are cheaper than deceased Magicians; current favorites more expensive than past favorites.  With anything, it pays to shop around. 

Here's a few ways to navigate eBay and locate this type of material:

1. Search by a Magician's specific name, like "James Randi" or "Eugene Burger".  When it comes to common names like David Copperfield, it's best to search with limitations, such as "David Copperfield -Dickens", or "David Copperfield -DVD"or you'll have to wade through extra stuff 
2. Search by word combinations such as "Magician autograph", "Magician autographed", "Magician signed", "Magician signature", "Magic autograph", "Magic autographed", "Magic signed" or "Magic signature"; this creates lots of options and is the method I usually use
3. Search by category Collectibles>Fantasy, Mythical & Magic>Magic.  From this listing, search sub-categories "Magician Memorabilia, Ephemera" or "Books, Lecture Notes" or "Posters, Prints" for the broadest listing of items; I keep this on my favorites for quick access.
4. If you have too much spare time, check out every listing under the subjects "Magic" and "Magician", because some sellers don't mention autograph in the title; that's where hidden surprises lurk.

Third, build your collection for pleasure, not profit.  If you must buy Magician autographs, consider it recreational spending, rather than an investment.  Nobody ever got rich buying and selling the autographs of Magicians.  Although recently the Jay Marshall auction has several cool lots which sold for top dollar, and immediately were broken up and offered individually on eBay at much high prices.  Regardless, the hobby has its own intrinsic pleasures. 

Autograph collecting is a doorway into the biography of history.  If you review Magician's autographs on eBay, you learn alot of interesting  anecdotal details about famous Magicians, because eBay lets sellers write their own listings.  Plus, when you acquire different autographed items, you can enjoy the art and design of each piece. 

Fourth, protect yourself from flaky dealers and fakey autographs.  Always read item listings carefully, so you won't be disappointed when you buy.  Review return policies, in case you don't like what you buy.  Check out shipping policies too, because you don't want your item damaged in transit (posters and oversize items are notoriously difficult to ship without damage).

Ask questions if you must.  And before buying anything, check out a seller's feedback ratings on eBay.  Dig into their statistics, especially if there is any negative feedback.  Even a good deal isn't good enough when it's offered by a questionable seller.

Fakey autographs are another problem among Magician's autographs.  Here's a few examples to watch out for:

1. The "preprinted" autographed photo is a copy of an autographed photo.  This fake is openly sold on eBay and usually the dealers label it clearly, but it's still a fake nonetheless.  Avoid it like the plague.  It can be detected if you shine a bright light on it, and bend the photo slightly.  A real signature appears to float above a glossy photo, while a pre-printed signature looks flat.  There's some Criss Angel and David Copperfield contemporary preprints selling these days.  Buyer beware!  I've also seen some vintage Mark Wilson fan club photos and membership cards that have a preprinted signature, but nothing contemporary of him or Nani.
2. The "stamped" signature is a rubber stamp on a photo, usually evident by a fuzzy thickness of the autograph lines from beginning to end, and sometimes a smudge on the photo; most common on vintage photos.  I'm sure these items exist, but I have yet to see a stamped magician signature.
3. The "secretarial" signature is difficult to detect, because it comes from the Magician's own office; Houdini had a secretary who signed some autographs for him; only experienced dealers know the difference. 
4. The "forged" signature is the most insidious fake, when someone tries to fake an autograph for criminal gain; the only way to tell is through an analysis of the autograph, and a thorough comparison to known authentic examples; any expensive autograph is suspect.  Houdini is the most forged magic autograph, because he is so valuable.  I heard that magician Jay Marshall was an expert at faking Houdini's autograph, although he reportedly only did this in a ball-point pen, for fun, because collectors know that ball-point pens didn't exist in Houdini's time.

Fifth, consider collecting your Magician autographs directly from the source, and buy tickets to see a real live magic show.  There's plenty of tickets for sale on eBay, especially for Las Vegas shows.  Most Magicians are nice about signing autographs after the Magic show.  When we went to Las Vegas, we had a great time meeting Penn & Teller, and Mac King, after their different magic shows.  They signed plenty of autographs for everyone.  Copperfield is the same way.

To learn more about individual magicians, check out my various magic-related eBay Guides including:

1. Andre Kole Autograph Magician Campus Crusade for Christ Andre Kole's autograph
2. Carl Ballantine Autograph Guide Magician McHale's Navy Carl Ballantine's autograph
3. David Blaine Autograph Guide and Collecting Secrets David Blaine's autograph
4. Harry Blackstone Jr. Guide To Autographs and Signatures Harry Blackstone Jr.'s autograph
5. Lance Burton Autograph Guide To Magic Collectibles Lance Burton's autograph
6. Ricky Jay Autograph Guide Magician Actor Magic Author Ricky Jay's autograph
7. Tony Curtis Houdini Autograph Guide Actor As Magician Tony Curtis's autograph

Whatever your interests, eBay is a great tool to build your collection.  My autograph collection sure has grown like magic!