Road bike shifter levers are different from flat-bar shifters. First the shifters are integrated with the brake levers. When shifting the bike you will be moving the brake lever side to side. This video starts with an overview of the levers and how they work and then moves into proper bicycle shift technique. You will learn about things such as cross-chaining and when to use the "Trim" function that exist on Shimano mechanical road bike shift/brake levers. This video is on the long side, and has a lot of content, so I have included an index below:
0:00 Start
1:15 Overview of Right and Left Shifters and Function
6:05 "Trim" Feature on Road Bikes (Lever View)
9:02 Proper Chain-line, Cross-chaining, and Trim (How They Relate Explained)
12:08 Proper Chain-line, Cross-chaining, and Trim (Demonstration - Chain and Front Derailleur View)
15:19 How to Avoid Cross-chaining - When to Shift in the Front
16:40 Front Derailleur - Avoid Shifting Under Heavy Load - Shifting on a Hill
19:20 Quick Tip when Going Up a Hill - How to Minimize Dropping Your Chain
20:39 Summary