A good latch (the way your baby holds your breast into her mouth), is the key to successful breastfeeding and the best way to ensure milk transfer and avoid pain and breast infections.
A good latch happens when your baby's mouth is wide open and grabs not just your nipple, but a good portion of the areola (dark portion of the breast surrounding the nipple).
A good latch is asymmetrical: your nipple is not oriented straight in your baby's throat (you wouldn't like having milk sprayed straight in the middle of your throat, would you?), but a bit upwards, towards the junction between her hard and soft palate. This is also the point that stimulates and keep suction active, when touched by the elongating nipple during baby's suction.
In a good asymmetric latch your baby grabs grabs more of the 'lower' part of the areola (the part near her chin).
Sit in a comfortable, semireclined (backwards)position
Try not to lean on the baby
Keep your baby very close to your body, at the height of your breast , with her ears, shoulders and hips on a parallel line (try drinking with your head turned one side: not so comfortable); make sure her spine is fully and well supported
Do not block your baby's head – hold your baby from the base of her neck
Your baby's nose should be at the height of your nipple and your baby's head a bit tilted back
Hold your breast with your index and thumb, not too close to your nipple (that part has to go in your baby's mouth); in case your breast seems to be very big for your baby's little mouth you can gently mould it in the same direction of her lips, like a 'sandwich' -- Imagine what you would do if you had to byte a big double layered burger (remember: moulding has to be done always in the same direction of your baby's lips: a good reference is to keep either your thumb or index parallel to your baby's upper lip)
Tickle your baby from her nose down to her chin with your nipple tip; while doing this you can keep your nipple oriented upwards, more towards your baby's nose than towards her chin
When your baby’s mouth is wide open, quicky bring the baby to your breast by pushing from her shoulders (remember: baby to breast, never the opposite!). Let your baby's chin touch your breast first, then her lower lip, and then only your nipple will enter her mouth.
It certainly seems like a lot of technical stuff, but with a bit of practice and help is is quite easy to do!