Most trees give warnings long before they fail. Knowing what to look for lets you deal with a problem on your schedule, not after a storm drops a limb on the roof.
Dead branches in the crown are the first thing to check. A few are normal. If a large part of the canopy is bare in summer, the tree may be declining.
Look at the trunk next. Deep cracks, cavities, peeling bark, or mushrooms growing at the base can mean rot inside the wood, where you can't see how far it has gone.
A sudden lean is a serious sign, especially if the soil around the base has lifted or cracked. A tree that has always leaned a little is usually less concerning than one that shifted after heavy rain or wind.
Location matters as much as condition. A weak tree at the back of a large lot may be fine to watch. The same tree over a bedroom or a power line deserves attention now.
If you're unsure, have someone look at it. Ramírez Tree Service gives free estimates across Fort Worth and Tarrant County. Call (817) 706-5649.