It isn't rude to judge people on a few things - shoes, handshakes, lack of eye contact and sheets, are some of the most important. Limp hands and bone-crunchers are on a par with sub-standard linen. So it is a home essential to start with replacing them.
The feel of crisp sheets is famously delicious, to keep this as an on-going delight invest in cotton sheets with the highest possible thread count that your wallet lets you get away with. The White Company have white (surprisingly) bed sheets available at reasonable investment prices. As do Muji's soft cottons in classic shades that creat a sophisticated simple design, with an addition worthy recycled element to gain you Brownie points all around.
We should all know better than to ever go over the top with gaudy patterns or anything (god forbid) designed by a former page three girl. But a reminder can't hurt. Colours should be neutral or pastels, how all men end up with black sheets at some point, is beyond me. Throw them straight out.
Keep bed linen subtle (and cuddly toys in the cupboard/bin) to start a sophisticated bedroom look.
A nod of humour in the right direction with your bed linen can just about forgive you for wearing a pair of last year's shoes (gasp!) A cheeky addition like Thornback & Peel's cushions could even let you get away with a lower thread count. It also helps you safely monitor any hint of a sense of humour in your visitors.