[geordief (OP)]

I understand  Black Holes come in different sizes.

Is there something they all have in common that  allows one to predict the tipping point when they form?

Are  they are all composed of the same kind of matter?

Do they all have it in common that light can never escape except by Hawking radiation?(if I have that right) 

[Halc]

I understand  Black Holes come in different sizes.

Is there something they all have in common that  allows one to predict the tipping point when they form?

They all form when any collection of matter is fit into its own Schwarzschild radius.  This sort of compression typically takes place during a supernova explosion, but it can be done by just making a large enough pile or rocks.

Are  they are all composed of the same kind of matter?

It isn't clear if they're composed of matter at all.  I mean neutron stars are composed of degenerate matter that is no particular element, but black holes have nothing that corresponds to what we know as matter at all.  It's just pure mass and charge at that point.  It still retains angular momentum.

Do they all have it in common that light can never escape except by Hawking radiation?(if I have that right)

Hawking radiation originates outside the hole, most of which falls right in, but sometimes half of the pair of new particles escapes.  They're formed by the gravitational potential of the black hole, so it counts as energy taken from the black hole if some of it can escape.  So I guess in a way it is mass/energy getting out, because it reduces the mass/energy of the thing.

[evan_au]

Is there something they all have in common that  allows one to predict the tipping point when they form?

Astronomers understand where black holes around 1.5-15 solar masses form: When a star much larger than the Sun exhausts its fuel, and collapses as a supernova. These stars blow away much of their initial mass in a violent solar wind, and even more in the supernova, leaving a remnant which collapses under its own weight to form a black hole.

A neutron star can maintain its own weight up to about 1.5 solar masses, so we don't expect to see supernovas leaving black holes much smaller than this.

Black holes can naturally grow by absorbing matter from nearby stars, gas clouds or other black holes. LIGO has observed the merger of black holes with masses of around 30 solar masses, forming a larger black hole with a mass somewhat less than the sum of the original masses.

But there is a bit of a mystery about how galactic-center black holes could accrete enough matter to achieve their current sizes within the lifetime of the universe. Some theories suggest that they formed around clumps of Dark Matter, but that is subject to some speculation.

There are theoretical micro-black holes with the mass of a mountain, that might be left over from the Big Bang, but none have been firmly identified to date.