Hmm, here are a few questions to ask yourself. These are qualitative
questions. But answering them will help increase your sales and hence
conversion rate.

Do I think this (is) a real and good company — the kind I want to do
business with, give my billing info to, etc.? Keep in mind, this is
not because you tell them you are a real company, but more the
impression you give with your site.

Do I think they have what I need?

Do I think they will deliver what I need reliably?

Do I think they deliver on time?

Is delivery/shipping free or inexpensive?

If I have a problem, do I think it will be easy to deal with them to resolve my issue?

Can I easily return something? Is it free?

Do I think they have good/the best/reasonable pricing for the product or service I am seeking?

Are they going to spam me if I give them my information?

Does it seem that this site is secure? Will they treat my information securely?

If clothing: Will this fit me?

Will I like it?

Do I need it?

What do others have to say about this product or service?

Can I try it out without committing?

Do I need to do this now? This, as with many of these questions, may be
thought about differently for different web sites. This may or may not
be on your home page, but it may be in messaging throughout the sales
process.