That you stay within budget.
That the site you are on /is/ the site you are on and you have no been rerouted to a scam page.
That the page you are on is /secure/ and has the little lock icon (with it shown in the locked position.)
That the number of items in your basket is correct.
That you make a copy of the purchase order & save it onto your machine.
That the shipping date is right and you know the last date you can return it.
That it is shipping to a /secure/ place for a package.
That there is someone you can complain to should things go wrong.
THEN & ONLY THEN - click the button
K? Let's be careful out there, people!