There is no point in defenders running backwards allowing the attacking player to push you down the court. This happens when some players think they are 'zoning' or 'restricting' the attacker.
I don't know how many times I see this happening. I'm not sure where this comes from or why defenders let it happen. The defenders job is to stay close to her opponent NOT play chasey with her.
Defenders should be adopting the side on or side by side style defending and this way you are with the goaler, not being 4 metres in front of her giving her free reign up the court taking passes and throws at will.
As a defender your job is to stay in the contest. You must learn to use your outside arm to defend - anything other than that you are going to be called for contact.
Be aware that as a defender you're going to attract the umpire's full attention all of the time.
If you can tap a ball on the rebound you can catch it, as there is no point in tapping the ball out of court, as you're only given it straight back to the other team for a throw-in close to goal.
Some defenders just don't think about what they are doing, it's not just a matter of running around hoping you'll get the ball from a bad pass in. Your job is to put pressure on the goaler, make her day as hard as you can. Let her know that you are around. Never give her a free reign.
You know that it is a non-contact sport so don't continue on the path that has seen you penalised whenever you go near the ball. Use your noggin and think about how you can make the goaler accountable without offending.
If you are being called for contact, back off.
If you are being called for obstruction take half a step back to show the umpire that you are taking notice of what s/he is calling you for.
Stay on your toes, don't stand flat footed. You can't take off quickly if you're not anticipating the ball coming down.
Practise changing positions with the other defender if you are comfortable. Though, if you are a new partnership I wouldn't recommend it, learn to play with each other first. Get to know where you both are in the circle, remembering not to get in each others way. One to the top and one on the base line or one to each side of the circle.
Fill the vacant spaces in the goal circle, make the attackers work hard for possession, remember, use the outside arm. This again is something that should be practised at training and at home. You don't need a netball or another player. Whenever you think of it, thrust your outside arm out and across in front of you. Notice how far away from the body this action is.
Combine with your other defenders, using plenty of chat, which helps let your fellow defender know what's happening while she is concentrating on her opponent.
As a defender, you see something that you think can help your teammate chat about it when play is down the court.
I'm not a great believer in holding onto a skirt so that the other player can have a greater defending reach - it puts you out of the contest. How do you expect to be able to rebound or protect a pass-off whilst holding another's skirt or aiding your teammate in any tangible way?
If defenders practise jumping each night of the week they'd be surprised just how quickly the leap would become a strong high jump to use when intercepting not only passes but also assaulting shots on goal. The jump practise must be plyometric to increase height. The fitness & Court Skills ebooks go into detail about specific plyometric training for netball.
Defending is fast foot work, a good leap and stretch with a lot of hassling.
Don't leave everything up to your fellow defender, guide her if needed, or better still get in there and have a go, support her. You have to work as a team/duo NOT as individual defenders.
Don't be afraid to hassle and mix it up. Regardless you will be pulled up by the umpire - it is going to happen. It is your job to try and stop the shooters from scoring.