Communicating with your child gets harder as they get older. I have 2 girls of different ages the eldest is 12 and in the second year of high school. The youngest is 4 and started school in September; she is the easiest to communicate with. Although she is very opininated and knows her own mind she more or less believes everything her parents tell her unless her big sister steps in (we won't go into that).
I believe you don't lie to your children if they are old enough to ask a question then they are old enough to have it answered. (it may have to be limited to their age). This I believe helps your child trust you and believe you will answer their questions.
I always tell my children that they should always tell me the truth and if they do that then we can sort it together. This seems to work as my eldest always tells me the truth. Some may not believe that but she does, although sometimes it may take her some time to tell me but it always comes out. I think this is because she trusts me because I always try to help but also because I know my child and know when something is up or not quite right. Why do I know this? Because I listen to her and ask her about her friends and how her day as gone.
I always tell my children I love them which makes them feel secure. My eldest is at the age when hormones are all over the place and her emotions can get the better. This can make life difficult as I still have to be her mum and tell her off and punish her etc but I also make a point of talking to her about things. I ask her if anything is bothering her and I find things out when she has her friends round as sometimes I will sit and talk to them for half an hour or something. Her friends are all quite chatty and open with me and I think that is because I show an interest and ask questions. Apparently I am a "Cool Bean" now that is quite something as it means I am cool and with it.
I believe the best way to communicate with your child is to be honest, some don't agree with this but it has always worked for me. Children are just people just like adults and they like to be kept in the picture. If you do this they will trust you more I have always told my children what is happening etc that way they feel secure.
I know a lot of adults think it is best to keep children in the dark and not tell them what is happening, trust me it isn't best always let them know what is happening so they learn to trust you from an early age that way as they grow up they will still trust you and let you know things.
To be able to communicate with your children you have to talk to them so they trust you and listen to them so they will let you know things. I know who my child fancies which is scary but innocent; but I know and I knew before she admitted it because I listen. That way I can keep an eye on things and know where my child is and with who. She also has no problem with phoning me when she is out for a couple of hours and it doesn't bother her if I phone her.
Because we communicate it is really good knowing she isn't embarassed if I phone her and she feels ok phoning me............ Or is that just because she knows she won't be allowed out if we can't keep in touch.