A few rules that you need to follow
1. Be selective over the clips that you use; people dont get impressed if you waste a whole clip on a sniper in trying to kill someone, only include kill's that are hard to do and will impress people. Such as lucky sticks, double's, triple's etc.
2. If your going to include single kills (which is not advised, unless the really are AMAZING,) then make sure you keep them as short as possible. Dont try to pad out a montage with lots of single kills, it's not big, nor clever.
3. DO NOT rush a montage. Montage's which have been filmed in a day are never any good, unless the player is amazing. The same applies for editing; you have to spend lots of time on editing a montage, to make it look decent. Last one i made, i spent about 10 hours editing a 5min 'tage. That was my first time using vegas, so with practice, it could be done a lot faster. Remember to NOT kill your montage with super heavy editing. Reasonably light editing done well will make a killer montage.
4. Learning what sort of editing works in a montage is great at helping you edit your montage to perfection. Watching other people's montage's is probably the best way of doing this, then learning how to do the techniques which they have used. There are loads of great tutorials online on how to do advanced editing techniques which will really make your montage stand out for the crowd.
5. Find a song to fit the montage. Music with beats is best for this, as you can sync the kills to the beats, so rock type music is most commonly used. Some music does NOT work in montages at all, you just need to delve into the depths of your music collection to find the pefect track. Also, dont use songs which you have seen in a million other montages (linkin park being one), try to be more original than that, use a song which is brilliant for a montage, and hasn't been used.
6. The best montages tend to only include pistol/sniper kills (and sniper/BR kills for halo 2). People arnt interested if you can kill someone with a rocket, or even a shotgun. Skill comes in using the precise weapons (eg sniper and pistol), a montage full od doubles and triples with a sniper, would beat a montage full of killtacs with heavies, every time. Clips with other weapons CAN be used, but only if its amazing kills again. Generally dont include unless its a triple or more.
How to record your gaming
The easiest way to record your game's, is to use a game recording program, such as fraps, or game-cam. I find the best of the 2 being fraps, so I will teach you the basic way to use it.
Unfortunatly, I can't find the link for it at the moment, but feel free to add me on xfire and i'll send it you..
Anyway, once installed you need to optimize the settings with which fraps records at.
These are the settings which i record at:
You don't want to go to any lower quality settings than these, as it will make your overall quality suck. Also the button you choose for starting/stopping recording, and taking pictures, is all down to personal choice.
Fraps records in uncompressed .avi format, which leaves MASSIVE file sizes, (we're talking gigabytes), so you will need to compress your good kills into a smaller format and delete the bits you dont want.
The way i go about doing this, is when i'm recording on halo, if i get a decent double or something, i double tap the stop/start recording key. This will mean that at the end of my video files in the fraps folder, I will have a kill maybe worth saving. This saves me time as I dont have to trail through whole games to look for good parts.
After a few days of recording, you should edit out the good parts for later use. To do this, open up windows movie maker (it comes as standard on all window's pc's), if you cant find it, download it from http://www.download.com/Windows-Movie-Maker/3000-2194_4-10187903.html?tag=lst-0-1.
Now that you have it open, just drag and drop your clip in to the program, and navigate to the part you want (using the video player thing on the right) then press ctrl + L, to split the clip. Make sure you trim the kill at both ends, but leave a few seconds either side, so that you can add effects to the start/end of video when your editing your 'tage. Then drag this shrt clip to the bottom row of squares, and select 'save movie file' from the 'file' menu at top left. Save it as whatever name you want, and when selecting a location, organise a few files, to be double kills, treble's, sticks etc, so that your clips are all organised neatly, and save it at 2.1 mbps format. This is enough to keep a decent quality.
After a while of doing this, you will have enough footage to edit your 'tage. I suggest using sony vegas 7, which you can download a free trail of, from http://www.download.com/Vegas/3000-2194_4-10601642.html?tag=lst-0-2. A great video teaching you how to use vegas can be found at http://www.qskglobal.com/othervidz.php, and named ''QsK King's Sony Vegas 7 In-Depth Tutorial''. Make sure you watch the WHOLE video before starting to use vegas, trust me, it will help a LOT.
After your masterpeice is complete and saved as a movie file, upload it to a website. I would say, DONT use youtube, whereas use something like http://www.filefront.com or http://useruploads.mythica.org/. These both allow for larger file sizes to be uploaded (youtube's limit being 100mb, whereas mythica supports up to 200mb. Montages should always be in the highest possible quality, and youtube destroys decent quality, so make sure you use one of the alternative websites, so that people can download your montage in all its high quality glory.
Edit: After feedback I'm adding a few more tips.
Recording gives low fps, so disabling some effects or lowering others will bring it back up. You can always add -use00 to your halo target to lower your graphics ingame.
If your not planning on using audio from gameplay in your vid, theres no point in recording it, as it will lower fps.
Make your editing right, dont use billions of effects on every clip, most of the time it will just make your montage look tacky and over-edited. Think about what effects your going to use and where, syncing effects with music will make a montage look like its edited well. Montages can still look good with minimal editing, as long as its done right. Watch other montages and pay attention to how they have editied theirs.
For cracks for vegas look here. http://www.halo3forum.com/montage-video-help/115124-adobe-aae-vegas-photoshop.html
It includes cracks for photoshop, aae etc. I wouldnt recommend using aae untill you have a good feel for editing in vegas, and you want to add more complex effects to your clips.
If you need the cracked version of fraps, just drop me a message on xfire: agouranga