Hi in my experience, a few tips :-
1) if the item is visually attractive the listing should consist mainly of sharp, bright and colourful pictures. Auctiva's image facilities are well worth using. If you cannot take good photographs them ask a friend. A cheap camera (£50 to £100) is all that is needed as only a low resolution is required compared with capabilites of even the cheapest now available. Probably a lot cheaper second hand. Plenty of practise with lighting in particular is well worth the effort to achieve higher sale prices.
2) if the item is technical, clearly laid out statements of relevant information, even as bullet points.
3) terms and conditions should be as concise and friendly as possible and comprise no more than 5 to 10% of the visible text on an average listing.
3) stick to simple clear fonts with minimal use of colours as many do not display or mix well, remember the eyesight of your expected customer age group especially if they are 40+.
4) keep backgrounds simple once again don't put off buyers who are older with plenty of cash and time to browse.
5) use Auctiva's scrolling gallery at the bottom of your listing and make use of their shop front, no I am not getting paid by Auctiva, they are very useful tools.
I would suggest you always look at completed listings of similar items and analyse why they did or did not sell, there are many factors not just over inflated prices. A few examples are rainbow fonts, all capitals, no punctuation, poor spelling, pages of conditions, dark, blurred pictures and no return policy.
Many other factors are involved but think of attention to detail and consistency of format as a worthwhike investment in your time which in turn translates in a greater return in cash