The usual term for the spaces in which spoken words are contained in cartoons is a "balloon". This is so called whatever the actual shape of the space. Lettering in a cartoon is an important feature, and it is well worth studying a few simple rules to make your cartoons look professional and easy to read. Firstly your letters should be very plain and simple. Compare them to the use of Arial or Helvetica typestyles in printing, or on the web. These two styles are among the most popular because of their plain, non fussy style, and are pretty easy to read in most sizes.
So, avoid fancy flourishes and curlicues, and capital letters should be the rule rather than the exception. You do not need much space between your letters in a balloon, but on the other hand do not crowd your letters and words. Make all your letters vertical, and avoid mixing slanting (italic) letters with vertical.
For the sake of neatness do not attempt to letter without first drawing some faint parallel guidelines, sketch the letters in lightly with pencil before inking. A good tip is to cut slots in the form of parallel guidelines out of a piece of thin card. A standard business card is ideal. Cut out two or three of these for letters of different heights. Use a pen whose point has become blunted with use for lettering. A new broad-nibbed pen may be used, but never a new fine pointed pen.
When you are lettering your cartoons, you should bear in mind that all drawings intended for publication, with rare exceptions, will be reduced in size before the printing process. Usually your drawing will be reduced by one half, although occasionally it will be a little more or less. So an original drawing of four by four inches will appear as a two by two inch drawing. The smallest type generally in use in newspapers and magazines is six point type, that is six seventy-seconds of an inch in height. So you can see that in a half reduction scenario you should be drawing your letters no less than twelve point type in size, or twelve seventy-seconds of an inch.
If the reduction is to be a bit less than a half then your letters should be drawn about an eighth of an inch high. Smaller type may be used sometimes , but it is always better to err on the side of safety and make your letters slightly too big, rather than too small. If you cut the slots in your card to these guidelines you won't go far wrong. You will never be thought the worse of (quite the opposite in fact, it shows professionalism) if you ask the paper or magazine you wish to submit to what reduction they usually use.
Finally don't forget that it is easier to sketch your words with pencil before inking. You can easily make changes which will not be noticeable, using a good quality eraser prior to inking.
Chris Haycock is an information publisher, one of whose hobbies is cartooning. For more information on cartooning, including details of a very special insiders course on cartooning, go to http://www.cartoonsforfunandprofit.com