Quick read. A continental grip and a repeatable toss are useful starting points for many serves. Practise one cue at a time, then include the next ball so the serve has a purpose in the point. Technique varies by player; pain is a reason to stop and seek qualified medical advice.
Try a continental grip for the serve
Hold the racket as you would a hammer and try a relaxed swing toward a comfortable contact point. The continental grip is a common teaching option for serving, as described in USTA's high-school tennis manual. A coach can help you judge whether your grip and motion suit your current skill and range of movement.
Make the toss easier to repeat
Start without swinging. Toss the ball toward a contact area you can reach without chasing it, and let an unsuitable toss drop. Notice whether your feet and balance stay steady. Then add an easy serve while watching the ball's path. A single toss cue is easier to check than changing grip, stance, and swing at once.
Practise the serve and next ball
Choose a service-box target, serve at a pace you can control, and imagine one likely return. If you have a partner, ask for a return and play the next ball toward a target with margin. USTA's yellow-ball coaching sample includes a serve-plus-one exercise. The target is a practice choice, not a guaranteed fix for double faults.
When to seek feedback
If the motion repeatedly breaks down, ask a qualified coach to watch the whole serve rather than diagnosing it from ball placement alone. If serving causes pain, stop and seek qualified medical advice; this page cannot identify the cause or prevent injury. For feedback on your stroke, see private tennis lessons. You can also use the solo practice guide for target work.
Serve technique questions
Is a continental grip required for every player?
It is a common starting grip for serve instruction. A coach can check how it fits your motion; this article does not prescribe one motion for every player.
Can a toss change fix my double faults?
A steadier toss may help you test consistency, but double faults can have several causes. Watch the full serve with a coach if the problem continues.