Here's a rough guide to calculating targets. On the examples shown , it's very hit and miss, but better than flying blind. It's very subjective as to where the bottom starts- not too hard, and what defines a pullback, from where the target is derrived.
Where there are multiple options, as in T3 base, use the last major low. Note how T1 and T2 have the same base, as do T3 and T4. Clearly T4 fails at the double top at 8610.
We also discussed that at this point , the market was trying to resolve the price around 8600/8610, arrived at by the fact that the price neither broke to the upside nor the downside.
The "classic " targets are much simpler and more clearly defined- Triangles "big" bull/bear flags, H&S etc. Just remember that a bull triangle that fails still has an equal magnitude target to the downside, form the support failure.
Often you will find that one target will lead you to the next as in T1 to T2. i.e. When T1 is reached, T2 is already developing. There is no point in trying to find targets that are 50+ points away- these are rare, but occur in exceptionally strong moves. Equally, don't bother with a target of 15 or less from the base of the pullback. It will probably end up just a few points above the last high- no use whatsoever.