[mothered]

Do you have a better or lower success rate, or would it depend on store?

It depends on "you", the SE'er- whether you've thoroughly researched the company, evaluated the Information accordingly, formulated your method based on your findings and executed the attack effectively by leaving nothing to chance.

In your experience, whats 3-5 things you usually look out for in a company when SE'ing?

This Is a basic formula to work with when SEing companies.

(1). Research/Information gathering (terms & conditions, company Internal processes & procedures etc).
(2). Evaluate the Information and Identify the pros and cons.
(3). Prepare/formulate your method based on your findings, Inclusive of the nature of the Item.
(4). Execute your attack accordingly.

Remember that a company's response and actions taken, Is based on what "you" have supplied them with. Given them no reason to raise suspicion, and your SE will succeed.