4 things really make a web store IMO,
First of all is the way the website is categorized. By this I mean putting all of the tips, tip tools, shaft maintenance, balls, etc. all on thier own pages based on catagory, it reduces clutter and helps customers find what they are looking for. It's also nice when pool cues can be sorted through based on brand and on price, and having "we recomend" pool cues is always a good way to help beginners. Another good idea is to always have an "other things you might be interested" spot on each product page. I always like browsing and finding something and going "hey! I didn't know they made that!"
Second is very key, pictures and descriptions. Every catagory should have its own page, and IMO almost every product you sell should have its own page as well. Included on the product page should be a nice LARGE/CLEAR photograph as well as a brief description of the product including what it does (if it's an accessory). Many web sites assume customers already know what they want and are just price shopping, this is wrong. If I could only count how many times I've bumped into something on an online store and said "hmm that looks interesting, I wonder what it does", but to no avail could I find out. One thing to add on to that is that I just recently purchased a cue case online for my brother, and it drove me nuts not getting to see (or know) the layout of the interior, whether it had deviders or tubes, and what they looked like. (hint, hint

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Third is the search function. I like being able to type in tip tool, and have my options line right up for me (coupled with good descriptions and pictures makes shopping and deciding which product is right for me a breeze!) The search ideally would be able to display items based on things such as best matches, highest priced, lowest priced, and popularity.
Finally, be clear on everything. Make sure all shipping information is out in the open, possibly on its own page, unless you are calculating shipping costs per item. Also, phone numbers, email addresses, street addresses, the more ways a customer can contact you the more secure they will feel about thier purchase. I feel that two links that need to be on the top of a web store are, "about us", and "contact us". This puts the information right there for the customer, no searching for little links at the bottom of the page.
Some that would be great to see you carry?
-anything made by Porper I'm a fan of, cases to tip tools
-one of my favorite purchases of late, the cue claw, carry it in muliple sized and colors and I can guarantee that I will at least purchase one from you
-Tips, individual and in bulk, the greater the selection the better (I like to try new tips out, still havent found that "magic" tip, but I'm about to try a sniper

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-little things that are hard to find, pads (for under tips), tip protectors (to keep chalk out of your case), table dots, and novelty items.
-billiard related clothing, t-shirts, hats, but nothing cheesy
-Oh and this one is very important, you need to only carry low and Mucci cues, and none of those straight ones!
Thats all I've got for now, hopefully I've been able to help ya out a bit, I look forward to see you website up!
-Justin (despotic)