How to network with agents
First of all you must remember that without actors agents would be useless, they would get no income and and be redundant. An agency needs actors like you need an agent, so keep this in mind when you are looking for an agent, they will want you if you are right for them and their books. This means not being scared of approaching them, or and 'selling yourself' in a professional manner. It is a two way agreement, they find you work and you pay them for it!
Ok, so let's think where agents spend most of their time? In their office, in the theatre, socialising and networking themselves. So find out where that particular agent's office is and post them a card with your credentials on there, or look at their client base and see who is opening in a show and try get tickets to the show so you can get to the after party/press night party, this way you are just bumping into them in a social way, congratulate them on their clients performance and then you have a few options (IN MY OPINION) You can go for the kill and ask them if they are looking to open their books and say you're interested or you can talk to them on a social level then leave before you get awkward, then, a few days later write to them referring to your meeting and ask for another more formal meeting/audition, or send a show-reel if you have it and mention when, where you met. This way they will remember your personality not the fact you were after something from them.
I know of actors who find an agent's favourite coffee place and 'accidentally' by chance meet them there and complement them in some way or other, "I saw your client in this show", "I hear you run a great agency, are you looking for a passionate actor such as myself?!"
You may think this is taking a risk and you're right, but what is the worst that can happen? They say no, were not taking submissions and you thank them and then when you meet another time you keep it on a social level, then try again a few months later. Take a chance and then you can say you've tried at least.
I recommend checking the actors that are already on the books, check their website, as if they have someone or many people similar to you they wont need another one! So do your research!
Do you have a friend at an agency who can invite you to the Christmas party for example, that is a way in to meet and be introduced to an agent.
Think outside the box with this one, where can you meet an agent that's not a formal meeting, in a cafe that you both 'happen' to use each day? Somewhere that's informal. Ask friends to be invited to press nights where there will be lot's of agents watching their clients, again do your homework.
There is a line between showing you're passionate/creative and meeting an agent in their local bar and saying hello, and stalking them. Do not invade their personal space, use your common sense and initiative, take a risk but do not push it too far.