Q:

How do you beat an opponent that can read your moves? 

How do you beat an opponent in a fight, who can read your mind and therefore knows what you're going to do before you do it? 
For example, in the video game Metal Gear Solid, an opponent called Psycho Mantis is initially invulnerable to bullets because he can read the player character's mind and so dodge the bullets before they're even fired.  The way to beat him is to

plug the controller into a different port

But this is very much breaking the fourth wall, which I'd like to avoid if possible. 
My current thoughts are that we can weaken this opponent by imposing some constraints such as:

They can only read one person's mind at a time, so ganging up on them would work
They're cheating and not actually reading your mind, rather doing something else that can be disabled or has a margin of error (if so, what?  Maybe looking into a possible future?) 
You can use the environment against them; e.g. make them so focused on dodging your immediate attacks that they are backed into an environmentally dangerous position

But I'd rather these were't too arbitrary. 

A:

Just because he knows what you'll do now does not mean he'll be able to stop you. 
If you've ever trained in martial arts you've seen this scenario a thousand times: you are paired up with someone and asked to train a particular move.  You do the move, then go back to your positions and repeat.  You know what is going to happen beforehand but despite that it'll go slightly different each time.  Sometimes your sparring partner will "beat" you and sometimes he doesn't.  This actually becomes more pronounced when two more experienced partners spar, as they will know what is going to happen and then see if they can alter the outcome by reacting to them.  They'll instantly abandon the move they were going to do if they notice their opponent standing wrong or trying to anticipate. 
In short: If my enemy knew what I was planning and anticipated for that, I would change my plan based on his new stance and moves.  Suddenly the fastest way for him to deal with my moves is through his reaction time.  The same time it takes me to anticipate his moves.  His only advantage is knowing what EXACT moves I might plan while I can only anticipate for a large variety of moves he has available.  This is also a disadvantage as he'll likely set himself up to perfectly counter my move and leave himself open somewhere else. 

A:

Pray to RNJesus
Have an AI, or a man on a radio, give you a list of possible approaches.   Carry a random number generator and just follow its lead.   This will remove the essential advantage of this power.   Your opponent can't figure out what you're going to do before you do it, by reading your mind, if you don't know either. 
Don't fight fair
Most of the time, this power has a fairly limited range.   (After all, if it didn't, a user could for instance make a killing in the stock market by reading the minds of C suite executives and ... I guess you'd call it para-insider trading?) 
So take advantage of this.   Shoot the telepath with a sniper rifle from outside of their psi-range.   Send them a message (make them think they intercepted a private email to you, say) then when they go where you expect them to go, blow up the building. 
In general, brainstorm a plan that assumes as soon as your foe gets within range, they immediately become intimately acquainted with every detail of it.   The plan is designed accordingly such that, by the time that happens, their goose is already cooked.   If you're superpoweredly tough, and they're not, call in an airstrike on your own position before you enter contact range. 

A:

Muscle Memory
Most fights aren't thought about.  Most people trained in any physical activity rely on muscle memory, and the actions are reflex. 
Maybe this ability only works on people who are having to give conscious thought to their actions? 
Mental Feints, Improvisation
If someone knows about this power (or maybe suspects), they could be mentally thinking about punching you in the face; but they really kick you in the shin. 
The insane, drunk, or confused might do mental feints without thinking about it. 
Sometimes, this might be improvising.  The attacker intended to go for a kick, but at the last second improvised for a gut punch. 
Reaction Speed
Base reaction time for a human is 0.2 seconds.  The amount of time for a reaction to take effect (pushing a button, throwing a punch) depends on many factors: how far you're trying to reach, how heavy the load your moving, strength, and so on.  However, in many cases that additional time between start and finish of an action is less than the base reaction time. 
So, say your opponent has made a subconscious decision to go for a takedown hold.  Your hero sees it in his mind, instantly.  However, in the 0.2 seconds it will take for the hero to react to the new information, the takedown has already happened. 
Many unconditioned opponents (people who aren't doing strength or endurance training) move much more slowly.  So, in that case, their may be plenty of time to react to the new information. 
Or, maybe the hero also has an improved base reaction time (0.1 seconds). 
Mass and Inertia
Based on your stance (standing tall, crouched, fists in front of your face, fists in front of your gut) there is a performance envelope: in 0.2 seconds there is only so far a human being can move those fists to block an incoming strike (for example). 
How far is based on body weight and strength.  But, for similarly classed opponents, the performance envelopes are roughly well-defined.  Fighting classes teach you to recognize these performance envelopes in yourself and an opponent both, and take advantage of them (strike where the defender can't possibly move to block in time). 
Even with the ability to see the mind of the attacker, and enough reserve reaction time to do something about it, your hero is still subject to physics.  If he (or she) is way out of position (had his fists protecting his face, and the bad guy goes for the gut), there's just not time.