Grav-nading is performed by tossing a grenade in the air, then using the gravity gun to fire it. There are a two variations to this. The first is the nade cook. This is done by grabbing and holding the nade in the gravity gun while the timer runs down, then firing it at the appropriate time for precise placement. The other method is called long distance grav-nading. This is done by simply zapping the nade with primary fire instead of catching it first.
When performing this technique, you can initiate with either primary fire (thrown) or secondary fire (lobbed). Both have their pros and cons. The secondary fire method will be described here, as it is slightly more forgiving if mistimed. If you decide primary fire is the method for you, the basic technique is the same. You will just need to make adjustments in your timing and catch angle, plus react slightly faster upon releasing the fire button.
To summarize the differences, the primary fire method is marginally faster, but it is also easier to fumble during moments of lag. Primary fire will throw the grenade away from you if you miss. This reduces the risk of blowing yourself up by accident, but it also means you cannot recover the grenade. In fumbling a primary fire grenade you may have just provided a free grenade for your opponent to cook and fire back. Another difference is that a secondary fire nade can be converted to a long distance grav-nade mid-throw, while a primary fire one may not. In other words, you can wait until after you have lobbed the nade before deciding on which variation to use to fire it, which is quite useful in an extremely dynamic game like HL2DM.
Step 1: Prime the Nade
Priming the nade correctly is often overlooked by players trying to learn to grav-nade. If you just click once to lob the nade, you will have a much harder time putting the nade instantly into your gravity gun. To prime the nade, hold down secondary fire and do not release it until ready to perform the cook. If you have primed it correctly the hand holding the grenade animation will no longer be showing on your screen. Practise doing this and moving around with the grenade primed and ready to go. If you decide not to use a grenade after all, do not release secondary fire, but instead press the button for another weapon.
Step 2: Lob the Grenade
When ready to cook, aim up slightly, maybe about 20 degrees. This will lob the grenade in the optimum spot to catch it. Release the nade and it will be lobbed in to the air. When first learning, do not try to catch them, just observe the animation as it releases the nade. Notice that at one point in the animation the palm of the hand is facing you. This is the point at which you will switch to gravity gun and catch the nade.
Step 3: Switch to Gravity Gun
As soon as you lob the grenade you can switch to gravity gun. Sometimes during moments of lag, you will switch too fast and end up grabbing at air. To ensure the nade has actually been lobbed, wait until you see the palm of the hand facing you before making the switch. In order to get the timing down you must switch quickly.
Step 4: Hold Secondary Fire
Now that the nade is in the air and you have switched to gravity gun at the correct time, you need to hold down secondary fire on the gravity gun to scoop up the nade. Note that steps 3 and 4 have to be so fast they are almost simultaneous. As soon as the gravity gun is out, you should be holding down secondary fire to grab the nade as quickly as possible. If this whole process from prime to catch is done correctly, it should look like the nade almost went straight from your hand into your gravity gun.
Step 5: Cook and Fire
Once you have a grenade in your gravity gun, a ticking timer will sound. The timer ticks fast, so be careful. You have five fast ticks to fire the grenade. The longer you hold the nade, the less distance it will travel, but hold it too long and you will blow yourself up. The actual timing and placement of a cooked nade comes with experience. For now just practise by counting the ticks and firing it at various objects and opponents.
Step 1: Prime the Nade
This is performed in exactly the same manner as the nade cook technique.
Step 2: Lob the Grenade
When you lob the nade for a long distance grav-nade, the height of the lob will determine the the vertical placement you can achieve when you zap it with the gravity gun. If you zap the underside of the nade it will go shooting upwards. You will need to lob the nade up slightly to be able to do this. The opposite is true for zapping a nade downwards. To zap a nade horizontally, try to throw it right in front of you and zap it dead center.
Step 3: Switch to Gravity Gun
Again, you may switch to gravity gun as soon as you see the nade throw animation. Use the palm of the hand facing you as a guide for when to switch until the action becomes second nature.
Step 4: Adjust the Angle
Assuming you have lobbed the nade at a suitable height, you can now adjust the angle of the grav gun relative to the nade to place the nade exactly where you want it to go.
Step 5: Primary Fire
Wait for the nade to be "sitting" out in front of you before zapping it. If you zap it too soon you will not get the placement you desire. If you wait too long you will fumble the nade. Getting the perfect angle and timing to place the long distance grav-nade exactly where you want it may take some experimentation. Setup a target in a wide open area and practise trying to hit it dead on.
Almost all strong players use their gravity gun to give orbs an extra boost, giving them additional range and making much harder to catch. Once familiar with this technique, you should fire all your orbs this way. Fast orbs are not difficult to catch once you are used to playing with those that use them, but they are more challenging than regular orbs, and can be troublesome when dealing with more than one.
Note that the steps performed in this technique need to be performed extremely quickly in order to boost the orb before it gets out of range.
Step 1: Click Secondary Fire
Click secondary fire on your AR2 to fire the orb as usual.
Step 2: Hold Down Primary Fire
As soon as you have fired the orb, click and hold primary fire. This is done so that when you switch to gravity gun you will be firing it immediately. Perform this as quickly as possible, or the orb will escape before you can finish the technique.
Step 3: Tap the Gravity Gun Key
The easiest way to time the shot so that it zaps the orb is to spam the gravity gun key. This means tapping it repeatedly as fast as you can. Note that you should still be holding down primary fire throughout this so that the gravity gun emits several rapid shots. As you get a feel for the technique, you may get good enough to shoot a fast orb by timing a single shot with the gravity gun. Note however that this is less reliable, especially during moments of lag. Once you get used to this technique, it will become second nature to fire orbs this way and you wont even have to think about it.
The instant orb catch places an orb that has just been fired immediately into the gravity gun. Much like the fast orb, it must be performed quickly so that the orb does not escape the gravity gun.
Step 1: Click and Hold Secondary Fire
Click secondary fire on your AR2 to fire the orb as usual, but this time instead of switching to primary fire, hold down the secondary fire button after you have clicked it. This is done so that the catch function of the gravity gun will be engaged as soon as you switch to it.
Step 2: Tap the Gravity Gun Key
Perform this step much the same as the fast orb. Holding secondary fire while rapidly tapping the gravity gun will emit several secondary fire catch pulses so that your timing does not have to be perfect.
One of the functions in HL2DM is the "suit zoom" which allows you to magnify your view of the map. This function can be used in conjunction with the magnum to snipe with a makeshift scope.
Step 1: Hold Down Suit Zoom
With mag drawn, hold down the suit zoom key. It is recommended you move around while aquiring your target. Standing perfectly still with no peripheral vision is often a recipe for disaster, although it may work ok in a 1v1 situation if your opponent cant see you.
Step 2: Hold Down Primary Fire
With zoom engaged, hold down primary fire. The gun is now primed to fire when you release zoom.
Step 3: Release Suit Zoom
Once your crosshairs are on your opponent, release suit zoom to fire the mag. If your aim was good while in suit zoom, the shot will land upon release.