Design for Content
More recently than ever this has been something I ask for upfront before starting any design on a web project. Yes, Im guilty and used lorem ipsum to show where content will be, but unless this is a fairly generic blog template or standard expanding text aera, its is damaging to the design.
edit – example picture is not a real situation , just to illustrate a design being done possibly without content, this site was designed with content prior to design

When designing a website now, we really need the content first, in the example if you have an area with a promotion and I design it with a picture a short title and one short sentence (designed with no content from client), that will take a certain amount of space, and then a client sends the content for that area with 3 paragraphs of text then the size of the area will be all wrong and probably needs more focus on that piece if you have so much to say, then it needs moving to a more prominent place in the heriachy.
Show website mockups in a browser
Dealing with remote clients is something as a designer is something we can just about get away with, this means there are less (sometimes never) face to face meetings take place, so alot of visuals are shown via emails.
When showing a client a visual, it is always best to talk them trough an Idea and you must show them the ‘product’ in its natural habitat. Stationery = Printed, Web = on screen, etc.