Argument from Motion
We live in a world of motion, movement is caused by other moving things, everything that moves must have been set into motion by other moving things.
There cannot be an infinite regress of motion (like an infinite row of tumbling domino blocks where there was no first block and every falling block had one before it to knock it over in an endless row) and something static must have started the motion in the first place
- the unmoved mover.

Argument from Causation
Things are caused, anything that’s caused had to be caused by something else since nothing can cause itself.
There cannot be an infinite regress of causes, so there must be a first causer, itself uncaused
– the uncaused cause.

Argument from Contingency
There are contingent things, contingent things cause other contingent things otherwise there would be an infinite regress of contingency and thus a possibility that nothing may have existed.
An infinite regress is impossible.
So there must be at least one necessary thing.

Argument from Degrees
Properties come in degrees.
In order for there to be degrees of perfection, there must be something perfect against which everything is measured.
God is the pinnacle of perfection.

There are a couple of problems with this argument:

1. These arguments only get us to, if we agree with the arguments, an unmoved mover, an uncaused cause, a necessary thing and something against which perfection must be measured. If you choose to call that 'God' go for it, but that is far removed from the god put forward by Christianity, Islam, Zoroastrianism or any other known organised religion worshipping a monotheistic god.
   More steps are required to get to there.
2. Philosophically and logically an infinite regress is not possible. It may be an uncomfortable idea to many, but it cannot be summarily dismissed.
   An infinite regress may well be possible in some form we cannot comprehend currently.
   If infinite regress is possible then there need not have been a first cause or a first mover.
3. If infinite regress is impossible and there had to be a first cause and a first mover, shouldn’t god also have been caused and moved? Why should he be exempt?
   This is the fallacy of 'special pleading'.
4. Lastly, if a necessary being is necessary, I want to introduce you to 'Bob'.
   Imagine for a moment there exists a mindless, unitelligent entity.
   It has always just been there. It has always existed, it never came into existence.
   Let's call this entity 'Bob'. Bob doesn't respirate nor consume anything. It just exists mindlessly outside of time and space.
   The only special feature Bob possesses is it belches out singularities of pure energy at random intervals.
   These singularities of pure energy rapidly expand into what we would call a 'Big Bang' forming universes.
   Bob is an unmoved mover, an uncaused cause and a necessary thing. - No need for a God!