Minecraft wiki entry for Time-saving_tips, associated text: Always use the best tools you can afford. Iron tools work faster than stone ones, and diamond tools work faster than iron ones. Note that if it's early in the game and you only have half a dozen iron ingots, you cannot really afford to use iron shovels; you should reserve your first few iron ingots for a sword, a pickaxe and armor. But by the time you have your first diamonds, you should have stacks of iron, and then it's fine to use iron tools for all your everyday uses. A similar consideration applies once you have diamonds in excess.
Unless you have high-durability diamond items, always carry spare tools or the materials to make them. At the very minimum always carry wood, as that allows you to make crafting tables and emergency wooden tools. This helps you avoid wasting time on long trips back to your workshop or main storage. The only reason to return home should be to unload, or because you've used up all the resources you took with you, not merely to collect some minor spare parts.
Don't carry worn-out tools. Once a tool has low Durability, leave it behind at your base and make a new one. It doesn't matter if an old tool sits in a chest for a while before being used in a repair, and it's more efficient to repair tools in batches. This trick also reduces the risk of accidentally breaking a valuable tool rather than using it in a repair.
Treat low-durability tools (wood, stone) as disposable unless you are very short on resources. The small 'repair bonus' on these items only gives another half-dozen uses, which is probably not worth the time needed for a repair (however, taking advantage of the repair feature may save some inventory space).
Craft your hoes from stone, this will provide the same speed as other materials. Most of the time you won't use up their durability either and instead of searching for one, it's probably faster to craft a new hoe each time you enlarge your farm.