The trick to sketching is practice, practice and then when you have finished that more practice.

One of the main things that you have to learn when learning to draw is how to see.  Human brains are very good at taking visual information and embroidering.  We tend to take a very small amount of visual clues and fill in the gaps.  ie the following sentence will make sense:

Knig Knog cilbmed the Emirpe Satte Biludnig. 

Because the first and last letters are right our brains unscramble the rest automatically.  The same thing happens when we look at an object and then try to sketch it in 2 dimensions.  We often draw what we Think is there not what actually is.

There is a fantastic book called "Drawing on the Right Side of the Brain" by Betty Edwards.  It doesn't work for everyone but she is very good on the principles of learning to unlock the creative impulse.  Give that a try.

Alternatively take a sketch book and find your self a quiet moment (around 4 am is usually good as the marauding hordes are in bed )
Pick an object and then try to empty your mind of what you "know" it to be and instead try and see it a series of shapes and planes.  Practice reproducing these on the paper.  Forget about the perspective etc for the moment and just play with what you are drawing.

There used to be a fantastic book on perspective by Dorling Kindersley but I have scoured their website and it's gone out of print.  However it is worth having a look in the childrens reference section of the library/bookshop as these often have some great books on art and perspective.

Good luck.

I reckon that a shrink would have a field day with us and our work full stop. "So tell me again you like to tear up paper, yes!"

I have the opposite problem to you in that I find the human form quite difficult to do but cope better with objects, buildings and fantasy.  However I do think that the scary thing with drawing chairs etc is that they tend to be uniform and symmetrical which can be offputting if you are looking for precision. 

Having said that there is a general belief that if you tried to make Van Gogh's chair (from chair with pipe) then it would fall over as the perspective is totally shot.  And yet it is very definitely a chair. 

Don't be too hard on yourself and keep trying, I suppose it depends what you want to do with the sketches.  If they are layout ideas then precision isn't crucial but if they are design blue prints then it is more important.

I always console myself with one major factor, I recycle all my disaster sketches as pulp and it is incredibly satisfying to rip them up and drop them into a pot of water.  Now what would a shrink make of that!

not everybody needs to draw to visualize things it helps me to figure out unforeseens but i have watched people build whole houses with out a line drawn

You could always make your sketch it would not matter if it was rough so long as you have the basic shapes and ideas down. You can then make small notes to help you remember.

Sue

ooh that sounds really handy. So far I've been using masking tape on the walls and floors to get an idea of ideal size and heights 

""Drawing on the Right Side of the Brain" by Betty Edwards. "
Thanks, Charlotte.  That was a useful tip.  Shortly after reading this I went on to our county library website, found there were eight copies in the system, one on the shelves of our town library.  Not long after I was booking it out.  Very interesting!
Davido