Actually, allowing a bird's talons to meet or almost meet around a perch indicates the perch is too small of a diameter for that particular bird, as opposed to we humans trying to do chin-ups or pull-ups, where a full round grip might be better for you, but a bird that is used to gripping perches, their two longest talons (outside on each foot) should almost meet (5/8 of the way to 3/4 of the way around a perch), with its talons' points/tips being able to grip the perch and as Timothy mentioned, when standing flat-footed, its talons/nails should not be so long as to cause any other part of its foot to raise off of the flat surface.....while our grip is stronger in the 2nd trough 4the joints of our fingers (different for humans who exercise their hands regularly), a bird's grip, because of the way their foot is designed, exerts more gripping pressure with the tips of their talons, because that gripping pressure comes from their finger tips (the base of each talon, rather than the tips).....
Similarly, it might not be advisable to polish off/smooth off/round their nails/talons because smoothed/rounded tips will not have any gripping purchase & a bird that trusts in that extra gripping purchase might start loosing trust in its ability to grip/stop/land...and...if you are perceived as the cause of this loss, it could affect your interaction/trust with your feathered friend.....
When trimming a bird's talons/nails, carefully look at how the bird grips a perch and how you will want to clip/trim the talon/nail so that it is cut at suck an angle that while you have removed the sharp tip, you are going to leave the nail cut at an angle that will provide the bird a reverse angle tip to its nail/talon.....
I had posted pics of how to trim nails so as to save tour hand/arm/shoulder, but still give your feathered friend(s) a way to still hold its grip, but because of the groups image limitations, they got erased when I needed to post other things.....
For those members who have PM rights, feel free to PM me & in the mean time, I'll see about putting together a file about trimming with pics & I'll send you a PDF of it.....if you do PM me, be sure to also send a working E-mail address, because sending back files via PM also affects group limitations.....
It may be as much as a week before I get the file together & out to requestors...I'm not sure I've still got the pics I originally used & may have to go back re-read the original posts & re-build everything, so don't get real impatient...they'll be forthcoming, if you ask for them.....