Get shopping carts through the checkout lane
There's no guarantee you'll close the deal with your customers, but these tips will head you in the right direction.
1. Simple Navigation
Create a site structure that is straightforward and easy to navigate. Build it around what your customers actually want to accomplish.
2. Easy-to-Find Carts
In the real world, the shopping cart is always near the door. Online, the cart should be found at the top right corner of your page. This is not the place to be different or original.
3. Quick Checkout
Give returning customers a fast path though the checkout line. Don't subject new users to multiple forms. Checkout should be completed in at most four pages.
4. Open-Door Policy
Spell out as much as you can about who you are. That means your security policy, shipping rates, commitment to privacy, and contact info. Above all, never promise something you can't deliver.
5. Speedy Pages
A slow site chases customers away. Aim for a page load time of less than five seconds for a 56Kbps modem. Kill the useless animation and annoying splash screens.
You have missed the most important point. Users abandon shopping trolleys - because they can! It's no problem. There's no comeback. They aren't real trolleys. No one gets hurt.
Why consider it as a problem? It's no different from window shopping. More people can do it and more will walk away because they had no real intention of buying in the first place.
You have lots of good advice about how to encourage potentiall buyers to purchase, all of it valid. But where's the problem? In a different paradigm, people will behave differently. Just because they put stuff in an internet shopping cart, ther is no implication that they ever intended to buy. Many will be just testing the system to see what happens, to try to understand how it works.
It may be that with the most perfect system, most visitors will never buy, so expending effort to improve the percentage is not cost effective.
My point is, understand the motivation of users and fix problems that really exist.