Having a clear story in your head about what is happening in your scene will massivley help you evolve your scene. For example, if you know that your are creating an office for a busy accountant with a desk piled up with books then immediatly you are cunjured up with images of books with bent pages, pencils everywhere and half finished coffee cups.
Don't be frigtened to make simple changes, for example our acountant might have purchased a note book and written by hand 'Sales' on the front or leaving drawers slightly open as if theyve been shut in a rush.
Before you get the the small details making sure your key peices work together is crucail. If you can't find the exact perfect pieces that work together don't be frigthened to change them! There are now plently of tools availbe to help you, paints, sticky papers, polymer clay, nail art stickers and many more.
I find that acrylic paints work the best for most projects and you can get hold of them easiliy in most craft shops in a huge range of colours, combine this with tutorils on youtube and you can have that perfect marble fireplace in no time at all!
When you've got your fav items think about where they are going, how long they've been there and whats happened to them. If it was in your house what would it look like in five, ten years time? I know that in our house the carpets always fade in that strip by the front door and there is always that annoying dirty corner on the kitchen floor where the broom doesnt quiet get completely in the nook. Are there nooks and creavases that dust is bond to get stuck in? Has the paint worn away from the years of sitting at the table?
Watered down paint can be a gret way to add detail and depth to a piece. Take care to start light and slowly build up - the dirty wouldnt have got there over night so your ageing process should take its time as well. For light furnture use colours like black or brown with touches of green whilst dark furniture will need grey or white touches.
Don't forget your cup of tea! Hold the milk and it makes the perfect aging assistant. Dissapearing into gaps and highlight flaws it has a natural quaility that is difficult to emulate in any other way. Experiement with wetter and drier tea, thicker and light coats, dry slowely or speed it up with the trusty hairdrier, it really is one of the greatest ageing tools.
If its your dollshouse that is having a cup of tea, think about using a scenic water to fill you cups as well as other places you might find liquids, maybe a fish bowl, glass of water by the bed, or a spill on the bathroom floor.
Dust and gunk is an avoidable in most houses, using different scenics mixed with glue or tea can make a huge difference. Maybe add a mossy stain to a outdoor terracotta pot, or a gathered dust pile under a sideboard! They can even be used to add earth to a pot plant. Flour and corn flour are also great tools for adding life to a scene.
As well as adding taking away can be a vaulable skill. A very fine grade sand paper could be used to distress and add history. I like to wrap a very small peice around a paint brush or pencil to try and keep the scale right. Take your time and step back often, again really thinking about the story of the peice.
Atompshere, texture, and detail are all really important, but remeber nothing is perfect in fact the is life of your scene will come from the imperfction so have fun with it and enjoy experiementing.