Your question is very broad, since it really does not specify what these weapons are to be used for. Just like here on Earth, you have a large assortment of weapons to deal with different target sets - an infantry team can carry an M-3 "Carl Gustave" to use against bunkers and lighly armoured vehicles which their m-4 carabines won't affect, but the platoon also has machine guns for suppressive fire, a Javelin ATGM to use against tanks, hand grenades for close quarter battle and so on.
Certain consideratons will apply for any sort of weapon (outside of handguns and personal defense weapons):
Space is open terrain. You have essentially unlimited sightlines and the adversary has very limited options when evading observation. Even being in orbit around a planet does not help, and using large numbers of sensor satellites and vehicles negates even that limited condition.
There is no stealth in space. You are operating against a 3K background (i.e. 3 degrees above absolute zero). Even unmanned vehicles will need "hotel" power for on board sensors and computers, and have to radiate away waste heat. Once the vehicle goes active with drives and weapons, it will be a brilliant spot against the cold background of space. Your constellations of sensors will also make it difficult to reject waste heat in a "hidden" direction.
Space is a vacuum. This means there is no fluid medium to react against. You must use rocket power or access some sort of momentum exchange in order to change directions - no swooping X-wing runs. This also means there is no practical reason to have "fighter" craft - aircraft work in different media than ships, which is why an aircraft carrier is useful on Earth. In space, a larger craft can carry more powerful engines and rection mass. The Space Battleship Yamoto can literally outrun space "Avenger" torpedo bombers in a battle.
Orbital and interplanetary speeds are enormous. Orbiting the earth requires a speed of @ 7km/sec. A rifle bullet moves at a leasurly 900m/sec, while a more energetic tank round can move at 1200m/sec. Since kinetic energy is determined by speed, even wadded up toilet paper can be dangerous in space, although rather impractical. Objects moving at orbital and interplanetary velocity pack enourmous amounts of kinetic energy, so even a "shotgun" pattern of ball bearings released in the path of an orbiting satellite can destroy it.
The Rocket Equation. This can be summed up by saying "every gram counts". For space vehicles this means they need to have as little mass as possible, consistent with the mission. You won't see elaborate space battleships, but rather "eggshells with sledgehammers" - weapons platforms with the most powerful single weapon they can carry.
Given these parameters, we can see what sorts of space weapons will be out there in "reality". Since smaller weapons have the best performance, in the near term they will likely be similar to the 1980 era "Brilliant Pebbles" proposal. This was to be a network of individual missiles in orbit (each one about the size of an air to air missile), supported by a system of sensors in higher orbit called "Brilliant Eyes". Between 800 to 1200 missiles would be needed to ensure complete coverage of the Earth.
1980 era Brilliant Pebble concept. The missile is shedding the protective "life jacket" to intercept a target
This is a relatively "low speed" system, with the interceptors moving at 7km/sec and destroying the target with kinetic energy by ramming it.
Farther in the future, we might want to have greater coverage, fire more munitions against "swarming" targets or to overwhelm defenses, so a railgun or coilgun might be used. These use electromagnetic forces to accelerate projectiles at much higher speeds. The "Have Sting" concept would have accelerated projectiles to 15km/sec - twice orbital velocity, and possibly be able to engage targets out to the edge of the Hill Sphere. These weapons are much larger, and can be considered analogues to artillery.
Have Sting to scale with US Space Shuttle. Image from "The Unwanted Blog"
Moving a bit farther ahead, using nuclear energy to make compact, high power weapons. Third or Fourth generation nuclear weapons use the energy of the nuclear explosion to drive focused weapons effects, for example, accelerating pellets to 100km/sec, or creating shaped charge and EFP warheads capable of accelerating streams of liquid metal to a small fraction of c. A Casaba Howitzer uses similar princples to create a narrow stream of star hot plasma. This replicates the effects of a high energy laser without the heavy, expensive and delicate laser generators, optical trains and mirror.
This gives you the ability to create compact high energy weapons which can cover great distances very rapidly, and deliver huge amounts of energy even against deeply buried targets in moons or asteroids
The principle behind all third generation nuclear weapons: the immense energy is allowed to preferentially escape through the hole in the radiation case in the microseconds before the device is vapourized
Finally we come to lasers. While lasers can be useful at any time, for space we want to take advantage of the long sight lines, and create a laser weapon with enough energy to vapourize metal, ceramics and carbon fibre at a distance of one light second (slightly less than the distance from the Earth to the Moon). One second means you have a minmal amount of time between firing and seeing the results of your weapon, so the adversary has no time to take evasive actions or deploy countermeasures. With current understanding, a laser weapon firing in X ray frequencies will require an accelerator ring 500m in diameter to bring electrons to the required energy - so this is a "ground mount" on the moon or battle stations in orbit. The Xaser will actually be dangerous much farther away, but the longer time between firing and seeing the results will give the adversary time to react. Still, being "scorched" by an X-ray laser a light hour away will not be a confortable experience.
Ravening Beam of Death (RBoD) X-ray laser
Interestingly, one possible counter to such a weapon is to "fill the sky" with tens of thousands of small "Soda Cans of Death" (SCoD), counting on the immense kinetic energy of each individual "can" to cause damage or destroy the RBoD, and using the vast numbers to overwhelm the aiming, firing and cooling cycles of the RBoD.
Ultimatly, you would want to combine these effects by having a constellation of different platforms. The RBoD would be the centerpiece, due to it's long range and power. Rail or coilgun platforms would be in support, attempting to overwhelm the adversary RBoD with thousands of rounds in a short time frame (any rounds which destroyed adversary sensor platforms or other weapons systems would be a huge bonus). Smaller ships with 3rd generation weapons would be scattered through the constellation for close in defense, and of course thousands of sensors would fill the sky to provide a detailed 3 dimensional image of the battlespace. The entire constellation would be spread through a sphere about one light second in diameter.
Several websites cover this in greater detail, so I suggest you take a look:
http://www.projectrho.com/public_html/rocket/spacewarintro.php (this is the introduction to a huge section of the website)
https://toughsf.blogspot.com/ A great site with lots of interesting information about other aspects of space and futurism as well
http://www.rocketpunk-manifesto.com/ While sadly no longer active, there is a great deal of comentary and discussion about space warfare still available