There are many ways to count, depending on your goal. For example:
1. SLOWS AND QUICKS
This is not very effective for counting Jive, but if you feel so inclined, you could do it. An example would be: "QQ, QaQ, QaQ".
Note the use of the word "a" rather than "and", which indicates the duration of the count is either 1/3 or 1/4 of a beat, not 1/2.
2. BEATS
When counting beats, technically you're supposed to count to the number indicated by the time signature (4 for 4/4, 6 for 6/8, etc), but you don't have to. In Jive, for example, the time signature tells you to count to 4, but you can also count to 2, 6, or 8.
Coutning to two is especially handy for Swing and Jive, because you don't have to worry about the mismatch between the length of the measure and the length of the pattern. Everything works in twos. An example of this would be: "1, 2, 1a2, 1a2".
If you count according to the time signature, it's the most technically correct from a musician's point of view, but the fact that most beginning Jive patterns last 6 beats make it a very complicated prospect. Here's how it would look if you count two Jive basics (fallaway rock) in a row: "1, 2, 3a4, 1a2, 3, 4, 1a2, 3a4". It takes two basics (12 counts) before you repeat the counting pattern.
If you ignore the time signature, there's nothing wrong with counting the number of beats according to the duration of each pattern. For example, if you have a fallaway rock followed by a whip pattern, you could count to 6, then 8, like so: "1, 2, 3a4, 5a6, 1, 2, 3a4, 5, 6, 7a8". The only problem with this method is that it makes phrasing very difficult, but unless you're choreographing, you don't really need to worry much about that.
3. "BEATS AND BARS"
Probably the most challenging method of counting is "beats and bars" (that's beats and measures to us Americans), whereby you replace the first beat of each measure with the measure number. A simple (non-syncopated) example of this is: "1, 2, 3, 4, 2, 2, 3, 4, 3, 2, 3, 4...", etc.
Now superimpose a couple of Jive basics over this, and it starts to sound really complicated: "1, 2, 3a4, 2a2, 3, 4, 3a2, 3a4". Enjoy.
There are only two reasons you should ever need to use this method: (1) If you're choreographing, and need to count the number of measures, or (2) If you're taking an exam with a sadistic instructor.
4. STEPS
Sometimes the perfect thing to count is not beats at all, but steps. This method is useful for identifying a particular step in a routine (eg "When you get to step #7, stop!")
An example of counting steps in Jive is: "1, 2, 345, 678".
Salsa dancers are adamant about NOT counting steps -- There has been a movement over the past few years to drop the "123, 456" count in favor of "123, 567"... Which is fine. But you should know that it's not INcorrect to count steps. It's simply another way of counting. Every method has its strengths.
One quick footnote here: The one way I would NEVER recommend counting Jive is as it is written in the new ISTD manuals: "1, 2, 3a4, 3a4". It's the most ridiculous way of counting I can imagine. Whoever dreamed this method up should be fired.
Reagrds,
Jonathan