I don’t think there is much on tips or guides, a lot of it is really just chance. Players have made posts with their thoughts and ideas. Give me a second and I can see if I can find them again and link them, 

What have you learned 

There’s another somewhere where players are trying to figure out if horse breeds like certain types of treats

Picture basically means it's Wild Essence, there used to be a bar with it to show how “wild” it is but has since been removed. I think it shows you it may be more harder to catch? I cannot say as I've had horses on a yellow icon run on me but a red icon? I've gotten one no problem.

There really is no set percentage to use what item. Everyone is different but I've come to find out just using sweet treats or crafted treats ((so like alfalfa carrots but without molasses)) works best. I no longer use Petting as that takes energy. I personally never found luck with lassos and whistles nor do I recall what they all do. 

As Maki has said, there is a guide out there on what treats work best for capturing wilds but even using that guide? May not always work out. For example, just the other day I tried to capture a wild thoroughbred, I know their preferred treat, gave him one and on next one? He ran. Sweet treats, if the proper one they like gain 20% bond and you need 75(?)% to get chance to Call them to you but since I give them their preferred Sweet treats, I always get the call at 80% instead and it does not show up at 70%. I believe their non sweet treats but still a favorite? Gains you 10% bond.

Lately I have found treats to work the best, but they still are not guaranteed. 

I believe the lasso may make the horse easier to catch - for instance, change it from yellow to green for the little icon? But I've only had it work that way once or twice so I don't really use it anymore unless I'm just messin' around.  If I really want the horse I'll use treats, if I'd like it but don't want to use treats then I'll use the whistle - if it works, it will just call the horse to you. But sometimes it will work on the first try, or may take many more tries. lol.