Step Three: Balloons and CaptionsOnce you've created a nice looking block of text that looks like it will fit in the space provided, you need a balloon to put it in.
Make sure that you are on your Balloon layer:

(NOTE: It's not essential that you use layers in the way I describe, but it does make your life a lot, lot easier!)
Select the Ellipse tool (Shortcut: L)

In Photoshop, the two elements on the palette below are the foreground and background colours, but in AI, these are the Stroke and Fill colours. Whichever one is at the front is the one whose colour you are editing in the colour palette.

You can swap between having the Fill and the Stroke active by hitting X, and you can swap the two colours over with SHIFT-X.
For the most part, you're going to want a white Fill and a black Stroke. The weight of the stroke is up to you, but around 1 point is a good start. I've come to favour 0.75pt:

Now draw yourself an ellipse:

At this point, it's worth explaining the difference between AI's two selection tools. I've met people who've used the programme for years and never understood the difference, but getting to grips with them will save you a lot of time.

The black arrow is the Selection Tool and the white is the Direct Selection Tool - you can toggle between them using the V and A keys.
Put simply, the Selection Tool is for selecting whole objects (including groups) and moving or scaling them, whilst the Direct Selection Tool is for selecting and moving individual points within a path, or component objects within a group. You'll see an illustration of why this is useful a little further down.
There's no reason why you can't leave your balloon as a perfect ellipse, or even a circle, but this does look a bit mechanical. Probably the easiest thing to do is flatten the balloon slightly -- note that this method is not the same as simply squashing it with the scale tool, which would still result in a perfect ellipse.
Use the Direct Selection Tool to select the top point of the ellipse:

If you use the arrow key to nudge this point down, you can count the number of times you do this, then repeat the process on the bottom point, and nudge it up by the same amount, giving you a flattened ellipse:

I know this sounds like a faff, but you can re-use this balloon as many times as you want, now that you've created it.
Put your balloon on the artwork, and then your text on top of the balloon. One of the advantages of putting your text in a text box, as described yesterday, is that you can now position the left and right edges of the box so that it is the same width as the balloon, and your text will be perfectly centred:

Note that having centred your text, if you want to change the size of the balloon, you can use the Selection (V) tool to resize it, whilst holding the ALT key which will scale it from the
centre rather than the corner.
Then you need to add a tail. Balloon tails should, wherever possible, point at the speaker's mouth. It's not necessary for the tail to end particularly
near the mouth, but it should point in the general direction.
Whether you want to create a straight tail -- basically a triangle -- or a curved one, you'll need to use the Pen tool (Shortcut P):

A straight tail is simply four clicks to create a triangle (you should close shapes by joining the last point to the first where possible -- it makes PathFinder operations more reliable), whereas a curved tail is slightly more involved:
Click to start the tail, here I've started inside the balloon. Click again to form a second point where the end of the tail will be. Hold and drag to make a curve.

The bezier curve will be reflexive and will affect the next section of the shape, so hold down the ALT key and click on the point, at which point one half of the bezier handle will disappear:

Click back inside the balloon and again hold and drag to create another curve:

Then close the path by clicking on the first point:

Using the Selection tool (V), select both the balloon and tail by SHIFT-clicking

Go to the Pathfinder palette and click on 'Add Shape To Area':

Your balloon and tail will now appear merged, but will actually be two separate elements that can be selected individually with the Direct Selection (white) tool, or as a group with the Selection (black) tool.

(NOTE: CS4 changes the default behaviour of this operation and expands the group into one, non-editable shape - hold down the ALT key in CS4 when using Add Shape to create an editable group.)
Note that CMD-4 will apply the most recently used Pathfinder operation to the current selection, so you don't have to use the Pathfinder palette every time.
One of the easiest ways to create extra space for lettering is to crop the balloon to one of the panel borders. I favour top and bottom over left and right, but all four borders are acceptable. There are two methods of cropping balloons.
The first uses a different Pathfinder operation.
Create your balloon as usual, allowing the unused portion to fall outside the panel border:

Using the Rectangle tool (M), draw a box completely covering the part of the balloon you want to remove:

Select the balloon
and the rectangle with the Selection (black) arrow using SHIFT-click:

Now select Minus Front from the Pathfinder palette:

And the rectangle, along with the unwanted part of the balloon will disappear:

Note that -- as with the 'Add Shape' operation -- you can select and edit individual elements within this group using the Direct Selection (white) arrow. The same CS4 proviso applies.
The alternative method uses a Clipping Mask. I've recently come to favour this method, but have been told that DC in particular actively discourages the use of Clipping Masks. At the time of writing, this is sadly not an issue for me ...!
The Clipping Mask is a similar operation, except that you use the Pen tool to create a shape and only objects or parts of objects
inside the shape remain visible.
Create your balloon as usual and then draw a shape around it with the Pen tool:

The shape only needs to be accurate where it intersects with the balloon - in this case, along the top edge.
Select both the Pen shape and the balloon with the Selection (black) tool using SHIFT-click and then, using the Objects menu, choose Clipping Mask -> Make


Once again, the unwanted part of the balloon will disappear:

Using a Clipping Mask is slightly more involved, but has two advantages:
1) It means that you only use 'Add Shape' from the Pathfinder palette, so that operation will always be CMD-4, whereas Make Clipping Mask will always be CMD-7
2) It works for irregular and non-right-angle panel borders.
And that's pretty much everything you need to know about standard speech balloons.
Caption boxes, by contrast, really
are just rectangles. Unless you can exactly match the stroke weight of the panel border, I think it looks untidy to butt the boxes flush to the border, so I always try to indent them:

Beyond that, however, there isn't much more to them!
Since this has turned out a lot longer than I intended (and I've been working on it for the last hour and a half!) we'll stop here, and tomorrow I'll deal with non-standard balloons: radio, burst, whisper, thought, and so on ...
Cheers!
Jim