Probably the biggest item to share trust with a website visitor is actual pictures of staff or people. Seeing the face of who you will be talking to is a HUGE selling point. Correct spelling and grammar is another part that people pay attention to, especially larger businesses!
As far as abandonment, this is definitely money left on the table. We do a lot of consulting with eCommerce websites and on some sites, we've seen upwards of $30k in a month, of products left in carts. We always recommend a plugin of some sort to handle it. With that particular site, we saw 30% closure, so that's an extra $10K that they wouldn't have received that month.
The biggest issue that we see is the lack of some sort of capture method for the details. Generally, you would want to have the user enter an email address to START the shopping experience. This is counter to most shopping cart systems as they usually collect that data at the end of checkout - but if you ask for email address and zip code, and inform the visitor that it allows you to assist with their order and provide up to date shipping information - then you're doing a service to the client, and they are more willing to enter it.
For others, like in hosting, we recommend a popup of sorts that says "enter your email address and receive 10% off your order instantly". This would then feed directly to MailChimp for a newsletter and followup campaign. You then send an automated message from MailChimp with the coupon code (or show it on the screen after signup).
Now you can track your actual checkouts and see if someone used the email address during checkout and compare it against MailChimp. If they didn't, maybe it's time to send them a 15% off or 20% off one-time coupon.
Ideally, instead of discounts, you want to provide something EXTRA which would cost you less in the long run. Maybe provide them a free website transfer, additional disk space, access to templates for design (if you have an agency license), or 30-day trials on services that you can upsell later.
There's any number of ways of doing it, but the key is to get the email address early and then crosscheck that against the checkouts for the day/week/month.
