The first hiking tip has more to do with expectation setting than technique. If you normally hike at about a 2-3mph pace (which is pretty normal), expect to cover 0.5-1.5 mph when hiking up a mountain.
If the trail is good, your decent can usually be at your normal pace, but if the decent is rocky or tricky, expect to go about as slow down as you did going up.
It’s important to get rough estimate of how long you think you’ll be on the trail so that you give yourself enough time to get back before dark or bad weather. This uphill hiking calculator works well, but learning how to estimate your time in your head is a simple and good skill to have.
In general, you can expect the temperature to go down about 5 degrees F for every 1000 feet that you climb.
You’re going to want to check the weather for the mountain that you’re hiking. A simple Google search will usually do the trick. The important thing to note is that the weather is often colder and windier in the mountains, and the weather can change quickly.
If you are hiking above 5,000 feet or so, the trees will thin out and disappear as you cross the tree line. Once you’re past the treelike, the trail is more exposed, the winds are stronger, and the wind chill drops the temperature even more.