in a different question I asked about surviving early attacks and transferring to late middle game. Most people said banelings were the answer. I'm not sure I'm using my banelings correctly. unless they're burrowed and i pop them up as someone walks over them I don't seem to get them to ever work. how can I improve my usage of them anytime they're not burrowed and underneath an opposing force, both against humans and AI?
I feel partly responsible for this question so I'll try to get through it for you.
So there are three ways to use Banelings you probably haven't considered:
The most common on is actually #3, but I'll go through them in that order.
The Baneling spider mine is very similar to what you're doing right now, and has the advantage of lacking any micro. Simply burrow your banelings (usually spread out in a line), and right click the 'Unburrow' to activate autocasting. These means the Banelings will rise up out of the ground whenever an enemy unit comes near them. Since Banelings deal damage on death, this is a very effective technique.
The next technique is the Baneling drop. This requires Overlord Transport and Speed to be effective. Load your Banelings into Overlords and as you engage the enemy drop the Banelings on top of them. Since Overlords have low priority and fly, they are less likely to die before delivering their cargo. You'll often see this in Professional Matches, as its very effective vs Terran Mech.
The final technique is the "bread and butter" of Banelings, the Baneling shield. Since Banelings explode to deal damage on death and are high priority, there is actually no reason to ever attack with them. Instead Move M next to or through the opposing force (usually Marine) and the AI will naturally attack the Banelings (if it has been given the Stop, Hold, or Attack Move commands). This will turn each of your Banelings into 30HP shields for your other units, will still having them serve their purpose. This is actually viable even without speed. Additionally, Banelings are neither light nor heavy, so no unit has the advantage against them.
In general with banelings, unless you have them in the enemies mineral lines or something of that sort, you want to do a regular move rather than an attack move with them. They still explode when killed, so letting them get as much of a surround as possible before blowing up is almost always better than just blowing them up as soon as they hit the front unit.
Against melee units (especially with zerglings), send as few in as you can at once to get the job done, no sense in wasting them by over-killing. You may wish to actually detonate vs melee units as they will often be moved away from your banelings rather than attack them. Just try to be near as units as possible when you do so. Also, avoid letting a single zergling cause a baneling to explode when possible. You must kill 3+ zerglings per baneling to be at all cost effective.
Against ranged units sending them in waves is more important as not all of them will make it. To be viable against ranged units mid to late game expect to send lots of banelings to get anything done. 20+ banelings is not uncommon. Against a pure bio-ball I have seen a pro player use in excess of 60 banelings in the late game. Upgrades will help as well. Melee attack and ground carapace are the ones that apply to banelings.
With burrow, spread a few groups on likely attack paths. Ramps work especially well. This forces your opponent to bring detection or use a lot of scans to advance safely. If they don't, unburrow in the middle of their forces and detonate. Edit: If you aren't comfortable in your ability to keep a good eye on your minimap, you can also activate autocasting on unburrow as Tzenes mentions, although this will usually do less damage than a manually unburrowed baneling.
Speed helps against ranged units, as fewer will die before getting up to them. It is vital if you want to use banelings to help counter things such as terran bio-balls.
I've had some success against Terran players with banelings/speedlings. If they're turtling and a little behind on military size, you can use banelings to punch through their wall of Supply Depots and even if you can't take on their full military you might be able to run to their mineral line and kill a few SCVs. This can do enough damage to their economy to justify the suicidal nature of this attack and also keep them distracted with re-turtling while I get an expansion up and running.
Not sure how successful this tactic is against high-level players. Early marauders might make it difficult to get at their mineral line.