In short, I can gess 2 causes of noise when you change gears: the combination of gears makes the chain to be too "crossed", or you apply too much force while making the change. (Another possibility is that the derailleurs might be misadjusted)

GETTING THE CHAIN "PARALEL" TO THE FRAME
If you have, a bike with three chainrings (30, 42 and 52 teeth) and a cassette of 8 sprockets, (of 26, 21, 19, 17, 15, 14, 13, and 12 teeth) you should avoid to engage the two smallest prockets (12 and 13) and the small chainring (30) at the same time.
That's because the chain should be always as paralel to the frame as possible, otherways it would be rather "crossed". If this happens, it had 3 consequences:

- The mecanic eficiency decreases (as much as from a 95% to a 75%)

- The chains wears more quickly as it only would be working on one of its flanges.

- THE CHAIN SCRAPES WITH THE FLANGES OF THE FRONT DERAILLEUR, WHICH IS PROBABLY THE CAUSE OF THE NOISES YOU HEARD as you were scaling gears. Actually you can see the chain and the flanges nearer and nearer -Always keep an eye on the road-

These reasons leads us to avoid all these

"FORBIDDEN COMBINATIONS":

Chainring Sprockets
30 with 13 and 12
42 with 26 and 12
52 with 26 and 21

In my road bike (it has two chainrings and 8 sprockets) which still has old-style levers attached directly to the frame, when you are scaling gears with the small chainring, the chain begins to crape with the front derailleur before reaching a "forbidden combination". Then, you have to move slightly the left lever, just enough to move the front deraileur and stopping the noise, but without changing to the big chainring. My more modern hibrid bicycle with 3 chainrings and a chainring lever with fixed positions, lacks this flexibility, an you have to change gears as the noise appears.

SHIFTING GEARS BETWEEN CHAINRINGS

Now let's write the number of teeth of your chainrings and sprockets in the positions they have on the bicycle to have a clearer idea of the position of the chain, because the following can be confusing:


Chainrings 30 42 52



Sprockets 26 21 19 17 15 14 13 12


Imagine you are in the small chainring (30) and in the 6th sprocket (14) and you want to engage a "longer" gear, the next sprocket is forbidden for this chainring so you have to move to the next.
Then you'll have to to:

- WHILE keeping pedaling smoothly, but WITHOUT MAKING FORCE ON THE PEDALS…

- FIRST engage the medium chainring (42 teeth)

- INMEDIATELY act on the right lever and engage a bigger sprocket 3 positions to the LEFT from the one you had engaged: the one with 19 teeth.
If you avoid this step, you'll find the force you have to exercise on the pedals increases abruptly.
In the other hand, IF YOU EXERCISE FORCE ON THE PEDALS AS YOU CHANGE GEARS (CHAINRINGS OR SPROCKETS) YOU'LL PROBABLY HEAR THE CHAIN'S GROANS AS IT CREAKS OVER THE DENTS OF THE WHEELS. (Of course this shortens the chain's and the sprockets' lifes, not to mention you can jam the chain in the front derailleur, which is a quite unpleasant experience as the pedalier would get blocked). Anyway the quality of the modern material has improved greately and whit the shifters fine tunned you should be able to change between sprockets very smoothly without almost stop accelerating. (Changing between chainrings is still a delicate operation)

You have only to draw back two sprockets when you change from the 42 to the 52 teeth chainring because the difference of gearing between the 39 and the 42 is bigger:
If I guessed right the number of teeth of your sprokets and chainring, you should change from the medium to the big chainring when you've reached the 14 teeth sprocket ( 3rd from the right), and then draw back to the one with 17 teeth; you can scale till the 13 and then change to the 15 but this would be a steeper change -actually the difference between 42/15 and 52/19 is even smaller-

You will lose some speed on the process of gearing between chainrigs, so it would be a good idea to first overspeed your feet A BIT, as you would do with the engine of a car with manual gearing. Then, when you change gears, move your feet SMOOTHLY until you are sure the chain has engaged. NOW YOU CAN APPLY FORCE AGAIN WITHOUT RISK.

IF YOU ACT ON ANY OF LEVER AND THE CHAIN FALLS BETWEEN TWO WHEELS WITHOUT ENGAGING ANY, the correspondient derailleur is probably misadjusted. Take it to the mechanic as this may be a dangerous event if it happens in the middle of the traffic or might be cause of losing of your balance and make you fall if you begin to pedal violently.

I began using Look type cleats but now I'm very more satisfied with the SPD type: I find more lateral freedom on the feet and are softer when you try to free the feet (I keep them adjusted to the almost softer position) The only snag was I had to relearn to engage them as I wasn't able to find the position of the foot on the pedal. More over, now I can use mountain shoes and walk normally on the floor when I stop for a rest in a road bar.