I know the values of resistors if they are gold-colored at the end. When both ends are the same, such as brown-o-p-brown and red-x-y-z-red, I am in problems. How to know which side has the last colour and which side is the starting end?
I asked a similar question a long time ago here but the resistor chart which was mentioned there appears to have moved. So from its new home at itll.colorado.edu here's the diagram, as far as I can tell one band will be thicker signifying it as the tolerance band (no-one responded when I queried whether this was the case in the previous post above so if I'm wrong please let me know).
If the start and end bands are ambiguous, you can usually work out which is probably the right way to read them by seeing which way round gives you a valid E24/E48/E96 etc. value.
..and there's always 'use a multimeter' to fall back on when you're still not sure.
Amos provided the correct answer the time.
Since technology has evolved, I have found easier method: iPad. I use apps such as iCircuit, eTools lite and Ohm Work to find information fast for this kind of details.
When it is hard to say what the end is: use multimeter as instructed by mctylr.
In theory there is supposed to be a larger gap between the value bands and the tolerance band.
In practice small components and sloppy printing often make this gap very hard to distinguish. Some of the colors can also be tricky to tell apart.
You can try reading it both ways, and see which of them makes more sense. For example brown-orange-violet--brown would be 130M 1% which is a standard value (though a very high one) while brown-violet-orange--brown would be 17K 1% which is not.
My general conclusion though is that trying to read color codes given no prior information is an excercise in frustration.