There aren't really any guidelines, but after some years of experience, you kind of get a feel for it. Some things, like shovels, I tend to break when they have wooden handles. I use those for light digging, and my regular shovel has a super-duty steel head, welded onto a solid steel handle. It's as strong as anything, but not for those of small bicep. :)
Usually the price goes a long way in determining quality of comparable products. It's not foolproof though, so it's good to get to know good brands. Around here, there's a brand that has a breakage warranty, and without proof of purchase, you can return it to the store ad get a brand new replacement for free. I use this to advantage, looking for worn out eligible tools at yard sales, etc.
Materials have a lot to do with it.
Common Tool Handles
- Wood is cheap, strong, and can last on a well-made tool. It snaps and cracks more easily than other materials, and becomes brittle when weathered. Great for light-duty use such as for lawn rakes, etc.
- Fiberglass deteriorates in exposure to sun, but is pliable, hard to break, and can make good tool handles. Sometimes the ends of the handles grind off inside the tool head for me, and I have to reattach it.
- Steel handles are usually pipe, which is too easy to kink, and hard to fix without a welding torch. I like solid steel, but this is heavy, and unsuitable to many people. Steel rusts easily, so yearly sanding/repainting steel handles prolongs the tool's life.
- Plastic handles should be avoided, except on some small hand tools, where they are of a good enough strength that they don't snap off under regular use.
Common Tool Heads
- Steel is the most common, for a good reason. It's strong, ages fairly well, and can be flexible. Stainless steel is a plus, but expensive. Look out for cheap cast alloys coated in chrome, they don't last long.
- Aluminum is sometimes used, and is good for lighter applications. It is rust resistant, and lightweight, but not as strong.
- Plastic makes for a super lightweight, super light-duty applications, like lawn rakes.
- Wood is rare, but some folks use wooden shovels when they think there is danger of cutting into electrical cable. You can overcome this by knowing the cable layout before digging.
These are just a few of the more common I've seen, and quality will vary greatly, even within one type of material.
It takes practice, like anything. Try not to get handles with knots in them, for instance, or uncoated/painted steel. Other things to thing about could be, using one tool instead of another one more commonly used for that purpose. So in my area, the soil is hard clay. Most trowels aren't designed to handle this well, and are better for working in potting mix type stuff. I use one of these soil knives instead, as it's much better for prying, cutting, and digging in the soil in my area.