Getting paid to criticize existing products is one of my favorite things. Over time, I’ve noticed that my notes fall under three main categories:

1. Heuristics — are best practices being followed by default?
2. Are the business’ goals clear?
3. How can we delight the user?

Examples of each are as follows:

Heuristics / Best Practices:

• Is there a footer at the end of a website?
• Text and images — are they easy to read and understand on any device they’re rendered on? Are they in the location they’re intended to be in?
• Shopping cart placement — most buyers know to look for this in the upper right corner

Clarity of business goals:

• Each page has ONE MAIN CALL TO ACTION and it is easy to find, easy to read, easy to click on from any device.
• The viewer is ready to click on this call to action now — a.k.a. they have enough information to make the decision, and they are the correct persona.

Delighting the user:

• Shortcuts for actions that a user will do frequently. Eg. Saving their recently used search filters for reuse later; a star icon that filters search results for only favorited items;
• Animations that keep the screen clean, but offer just enough information that a user feels safe and catered to on a personal level
• Remembering things that typically stay the same for a user (eg. keeping a user signed in), while allowing frequent changes for things that will evolve (eg. search parameters)

I hope this helps. Go be (productively) critical.