Below is a list of all the Life Capsules you can get when playing the game normally.
First Cave. After visiting the Hermit Gunsmith, head straight up and you'll come across a pair of breakable blocks. Bust through them with your ●POLAR STAR● to reach this capsule.
Mimiga Village. Climb on top of the Town Hall, and make a jump from the roof into a gap in the hanging blocks on the right. Climb up and fall down into the small nook to reach this capsule.
Pipeworks N. After the Save Room, fall down into the water and try to jump over the drain stream. The current heading to the left should push you over the current that would suck you into the pipe, letting you reach this capsule.
Grasstown. From the Grasstown Tower, head right. You'll come across a tower of breakable blocks. Break the second and third ones from the bottom, then break the fifth and sixth ones. You'll be able to climb up these new gaps without trouble, to reach this chest.
Grasstown. After the Auxiliary terminal is turned on, activate pillars one through three, and ride the fans up. At the topmost set of fans, climb up and to the left to reach this capsule.
The Underside. After the Underside Shack, you'll come into an inverse U-shaped path, ending in a pair of girders opening upward to let you proceed. After this, you can see this capsule in the wall. Approach the gap in the wall below it to find a passage leading to it.
Eroding Valve. Climb up and to the right, following the hidden passage behind the paw-print blocks. You will see this capsule at the top after some tricky jumps. You can also return here after you get the ●BOOSTER v0.8●, if you miss it.
Sand Zone. To the right of the pit where the 'Flower' teleporter is, is a bed of spikes under some platforms, followed by a series of three broken pillars. Carefully fall off the left side of the floor onto a small piece of slope, and walk into the wall to reach this capsule.
Labyrinth S. After entering from Labyrinth W, fall straight down and you will see a breakable block on the left. Break through it with the ●MISSILE LAUNCHER●, and continue along the hidden path to reach this capsule.
Labyrinth W. After you pass the massive bed of death spikes while riding Monster X, there are a few breakable blocks on the ceiling. Break them open with the ●MISSILE LAUNCHER●, and carefully fly up to reach this capsule.
First Cave. After completing the Labyrinth, you can simply fly up and reach this capsule with the ●BOOSTER v0.8●. Alternatively, if you want to get it early, you can lure the Critter next to it down, and use it as a platform...
Sand Zone. If you got the Remote from Malco in the Labyrinth, head to the Save Room to the right of the 'Gaudi' teleporter. Open the shutter to claim this capsule.
Egg Corridor. After reaching Cthulhu's Abode?, exit through the door on the left, and head to the left to reach a pair of breakable blocks. Break them with the ●MISSILE LAUNCHER●, and carefully compete with Basil to reach this capsule.
Passage. Complete the Once-Sacred Grounds, and head up the passage to where the Seal Chamber once stood.
Plantation. In the middle of the second floor, there is a large piece of dirt suspended by three chains. Fly up alongside the second chain until you reach two individually suspended blocks, then climb past them to reach this capsule.