In years past a do-it-yourselfer who wanted seal doors and windows with caulk without a caulking gun was in for a very messy experience at best. Today there are a variety of caulks available in squeeze tube applicators that are designed for application without caulking guns. It is essential that you choose the right caulk for your particular application. Silicone is best for tile and window glass and any caulking that will eventually get wet. Latex, or painter's caulk, can painted over with latex paint so that it becomes invisible.
Select the color of caulk that best suits your application. If you cannot match the tile, or whatever you are sealing, match the grout lines to blend it in. Cut the tip off about 3/16 inch wide on an angle.
Grasp the tube from the rear, with the tip aligned to the seam, or other line you wish to caulk. Grip the end of the tube and curl it into your hand, dispensing caulk as you drag the tip along the line to seal it. Continue to squeeze the caulk out at a steady rate, letting off the pressure about an inch before you intend to stop the bead of caulk.
Put on a latex glove to prevent the latex sticking to your skin and wet one gloved finger in clear water. Smooth the caulk with the gloved finger to create a neatly curved bead, that overlaps the seam, or other line a little on each side.
Choose caulk that matches your paint or use white for easy cover up later. Cut the tube end off about 1/4 inch wide on an angle. Squeeze a small amount of caulk out to "prime" the tube.
Align the tip of the tube with the seam you are filling. Grasp the tube in your dominant hand and curl the end of it over to roll it down as you squeeze the caulk out. Run the tip along your seam on about a 45 degree angle, apply a smooth bead as you go.
Wet the tip of a finger in clear water and use it to spread the caulk evenly to provide a good seal. Add more caulk to fill any voids that appear as you work the caulk in. Allow the latex caulk to dry at least an hour before painting.