Let's set the tone here before we go any further - I have never owned a set of scales. If I had, I would probably have left them behind somewhere - and that goes for any other kind of measuring equipment. There are ways of getting by without such sophisticated gadgets. You won't go wrong if you follow three basic rules.
The first rule is do not attempt anything that will go drastically wrong if the ingredients aren't accurately measured out - you won't find any recipes like that around here.
The second rule is learn how to judge measurements roughly, using a variety of everyday containers and things you find lying around the house, which leads to the third rule.
The third and last rule is USE YOUR BRAIN. If a recipe calls for 500g of dried lentils, buy a kilo bag and use half. Remember that most packaged food has the weight written on it somewhere and when you buy vegetables, grains and pulses loose, you usually ask for them by weight. Liquid containers usually have the quantity written somewhere and not only is this useful for estimating how much of the contents to use, the empty containers can also be kept and used as measures (click here for metric/imperial equivalents).
Did you know that one millilitre (1 ml) of water weighs one gram? That's a useful piece of information when you think about it as it means that yoghurt, honey, oil etc. can be measured by volume, using old containers, and the volume converted to grams - it won't be 100 percent accurate but it'll be close enough.
Using spoons and cups is also a good way of measuring things. Recipe books often refer to 'table spoons' and I also occasionally refer to them. I also refer to 'soup spoons' and 'dessert spoons' because that's what I have and what I use. They're all slightly different in size, and I don't have a 'standard' tablespoon for measuring - I wouldn't know where to get one. What I do know - I remember this from home economics at school - is that 1 table spoon = 4 tea spoons.
In practice you'll get about three teaspoons of liquid into a normal dessert/soup spoon without spilling it. I know this because I've just tried it to make sure.
Cups are a vaguer concept than spoons simply because there are lots of different types of cups around and I probably skived off the home economics class that covered the precise details, because I don't remember them (there's a moral here, kids - always be sure to ask your friends for their notes if you skive off classes).
Suffice to say, a cup is not a mug. It's much smaller and sits on a saucer. The trouble with cups, however is they usually come in sets of four at least, saucers included. If you're like me, you're more likely to have a mug lying around. If so, work on the principle that a cup is about half or two thirds of a mug, depending on size (see rule 3 above).
In many recipe books they tell you how many people you can feed with a particular dish prepared using the measurements given. I don't always do that. I sometimes do, but not always. There are various reasons for this, not least the fact that some people eat more than others. Applying rule number three helps here too - you should get a fair idea of how much of something a recipe will produce by reading the quantities involved. Also, the recipes shouldn't be considered in isolation. Serve a variety of dishes on the table. Make more than you need for one day and serve what's left over the next day along with something new. Spiced dishes taste especially good after a night in the fridge and the combination of flavours from two or more dishes is always interesting. If you have more guests than you expected, knock up a quick salad and serve extra rice. There's also the health aspect to be considered ( see the section on 'Nutrition' for more details on this). The key to a good vegetarian diet is variety. This style of eating is popular in India, where people have been vegetarians for thousands of years - they know what they're doing.
When oil is specified in a recipe for frying I usually haven't indicated the quantity. Some people like a lot and some people like to use very little - that's up to you and the recipes are robust enough to handle a bit of variation (that's the whole idea actually) The same goes for salt.