For all of you who don't know a gemutlich is a warm and cosy surrounding. Its the sort of thing Eliza Dolittle sang about.
First, tidy up, throw away ruthlessly; and put a daffodil in a (very clean) milk bottle with water in it on the table.
Next, arrange the books on the bookcase so they are not too neat (they need to look used) but are vaguely ordered; buy some mattress ticking and cut it up to make a table-cloth, a throw or curtains (even if they are nailed up and then tied back with a ribbon); track down a blanket or rug and put it on the chair or sofa; tidy the kitchen, then put out a fresh loaf of bread on a bread board with a bread knife and some fresh coffee in a tin (for the smell alone, even if one does not use it); if possible, have bare boards instead of carpet or lino (if the boards cannot be stripped or polished, they can at least be painted grey or pale blue - although this might be pushing it in three-quarters of an hour, see below); have a pile of newspapers, books, knitting, sewing, anything to make the room look lived in; if there is no furniture, use wooden champagne boxes for anything from a low chair to a side table to a bookshelf; if unable or not allowed to get rid of depressing furniture, cover it with the mattress-ticking; and try to acquire one or two old things - a wooden box, a blue and white plate, a clock, a bentwood chair - as these will improve over time, whereas the cheap, modern stuff will deteriorate into tatt. To this end, it is far better to buy something old at an auction than to buy something new that will look grotty all too soon; magazines like Country Living and BBC Homes & Antiques are full of ideas.
Above all, aim for simplicity: the chic-est rooms are those that have the confidence not to look as though anyone has tried too hard. And for those who have more than three-quarters of an hour, the next most transforming thing is paint.