Hi Scott! Welcome to COMC.
My questions about COMC- first how do you spam your stuff for sale there? How do you get that link?
You don't spam it there. You can spam it here, by posting to the following board:
Spam your eBay & COMC listings here! (Photobucket, Sportslots, etc.) - Blowout Cards Forums
You can also spam your listings at the Facebook page:
Welcome to Facebook
Be sure to include a link to your store if you're posting on Facebook. You'd be surprised how many people don't. Also, it should be noted that, on Facebook, you can instantly remove your thread / post when it's no longer relevant or if it becomes too Spammy.
Presumably you can also chat up COMC on other discussion boards across the internet, provided you conform to their local rules.
I've seen people have there COMC ID in the side under their BO ID- how do you do that?
I sent in 30 cards to start after careful research into what was on the site and how much things were selling for. The majority of the ones I sent in are not in stock at all on the site or have 1 or 2 others with high prices. Is this a good way to go?
It's an excellent start. Personally, I'd rather focus on the actual price. If you'd be happy with the lowest price listed, and especially if you'd be happy with 1/2 of the lowest price listed, go ahead and send in the card.
In my experience, cards where there are lots in stock often sell very well. It's just that they will sell for the lowest price listed, or people will make an offer, possibly as low as 1/2 the lowest price listed. So they'll sell for a deep discount to guide, but they will sell. This is especially true if the card is a rookie card of a star player, which many of these are. Some collectors buy multiples of rookie cards when they can get them cheap enough.
One drawback of having a card in stock which others also have in stock is that they might undercut your price after you've undercut theirs. If yours is the only one in stock, you have more pricing power.