Since I'm a rec climber who goes in the woods, 99.9% of the trees I go up have never been climbed before. I like it that way.
Here's how I approach assessing the TIP, it's all about looking at the big picture as well as the details. Nothing's perfect but it's possible to narrow down the risk quite a bit. I'm no daredeveil. Every time I climb up on the first ascent of a TIP there's something something new to learn about tree health and structure.
1. Tree assessment = top to bottom inspection: roots and ground, bole, up to the crown, up to the tip top.
2. Bear in mind the species, for example red oaks are pretty much always screwed up in one way or the other etc., learn the pitfalls for each species and different age trees.
3. Use binoculars to assess the TIP and generally inspect the upper crown
4. Don't tie in somewhere stupid like 2/3 'rds out on a branch from the crotch or stem etc.
5. Bounce test: footlock on doubled rope without being tied-in (allows you a chance to escape if you bust out the TIP during the test), give a couple or more good bounces.
6. Use a smooth climbing motion, there's no rush rec climbing. No need to shock load the TIP on every pull as you climb up.
6. Climb directly to the TIP and inspect the rope placement and branch before making any further moves in the tree.
-moss