If you don’t have a lot of drawing experience, try copying or tracing a similar drawing or painting by an artist that you really like. This can help you learn how they make marks and approach their artwork.
Make sure the characters aren’t just standing there kissing. Put one character’s arms on the other’s lower back, under their jaw, or on the back of their head. You could also have them holding hands.
Use a mirror every so often to examine your drawing. This technique can help you see your drawing in a new way while also pointing out any obvious mistakes.
If the drawing program you’re using doesn’t have layers, you can use the paint bucket tool to make the sketch lines grey, then bucket fill them white when the outline is finished.
Notice the heart shape on the head outlines. Always remember that whenever you draw two people kissing on profile angles or side views, the outline sketches for the characters’ heads look like a heart shape.