One thing that helps a lot is making your tower base regular in its pattern, in way so that it has some sort of symmetry, ignoring slight differences to keep the tower standing straight and such. Don't just haphazardly plop down balls - the many irregularities will create points where your tower can crumple. Note that all the top 10 towers have some sort of order to their base's construction.
Players used to think that the most optimal way to build towers was two build them with gaps already in place, by having two legs join together higher up. This is how the towers in 3rd (a bit different from typical for bi-leg towers), 7th, 9th and 10th were built. Most towers are not built this way anymore, so you may have less help with this type.
The more common method now is to have a single solid tower and pluck holes in it to liberate gooballs. This is how the other six top 10 towers were made. These towers are (usually) made by building a spine with vertical sides that goes up the center of the tower until the pre-final rush, and as the spine is built, the triangle sidings you see (place a gooball on the vertical side, then attach it to the ball below with a new strand) are built with it (do not attempt to add these after!). Then you will have to figure out how to pluck the holes in the spine. Though sometimes holes aren't needed much, like in DaB's tower.
Building with few gooballs climbing on the base being built at a time can help prevent it swaying too much early on. But I suggest that you make sure you can smack the tower back upright with a thrown gooball if needed. You should also make backups of your profiles using GooTool so you can try different things or re-attempt the final rush as many times as you need.
There may be other things I'm missing, but that should be a good primer. Good luck
You have to have a sturdy base, and use less goo as possible. If you run out of too, get some from the base
One thing that helps a lot is making your tower base regular in its pattern, in way so that it has some sort of symmetry, ignoring slight differences to keep the tower standing straight and such. Don't just haphazardly plop down balls - the many irregularities will create points where your tower can crumple. Note that all the top 10 towers have some sort of order to their base's construction.
Players used to think that the most optimal way to build towers was two build them with gaps already in place, by having two legs join together higher up. This is how the towers in 3rd (a bit different from typical for bi-leg towers), 7th, 9th and 10th were built. Most towers are not built this way anymore, so you may have less help with this type.
The more common method now is to have a single solid tower and pluck holes in it to liberate gooballs. This is how the other six top 10 towers were made. These towers are (usually) made by building a spine with vertical sides that goes up the center of the tower until the pre-final rush, and as the spine is built, the triangle sidings you see (place a gooball on the vertical side, then attach it to the ball below with a new strand) are built with it (do not attempt to add these after!). Then you will have to figure out how to pluck the holes in the spine. Though sometimes holes aren't needed much, like in DaB's tower.
Building with few gooballs climbing on the base being built at a time can help prevent it swaying too much early on. But I suggest that you make sure you can smack the tower back upright with a thrown gooball if needed. You should also make backups of your profiles using GooTool so you can try different things or re-attempt the final rush as many times as you need.
There may be other things I'm missing, but that should be a good primer. Good luck
edit: I think this is the tallest tower that is 'random', which owes its height due that crazy final rush that constitutes almost a third of the tower's height: http://goofans.com/leaderboard/profile/c0f37f6ca4329717a07443b1f9eabade
My Top 5 tower[s]: 51.38m Profile | 51.17m Video - Click on my username to see my addins.