make a list, and group sins together, either by year (i assume it's a 'life confession') or by category (e.g. i just say 'i suffer from pride', rather than list every time i have manifested pride in the preceding month; my priest doesn't have 4 hours spare!)
it doesn't matter how you list them, but a list is useful to help you remember (and to avoid those 'oh no, i forgot to confess that big sin' moments as you approach for holy communion).
personally, i have not used a list as i seem to remember sins better than other things (i'm particularly bad at remembering friends' birthdays), but lots of people have told me it is useful.
my current father of confession has a way of helping me to remember, by giving me that 'are you sure that's all?!' look, but i am not sure if everyone has that.
maybe list the big things (abortions, tax evasion and other stealing, sexual sins, violence etc.) and group the others in categories (lack of prayer and Bible study and church attendance and fasting, pride, vengeful thoughts, lack of forgiveness, hatred, selfishness, greed, going on the wrong websites, lack of compassion, gossip etc.)
before confession, make time to go to God in prayer for repentance.
your church should have suitable set prayers (if not, ask someone here, who can point you in the right direction), and then add your own prayers. picture the very great thing God has done in creating the world, taking care of us, and then coming and suffering for our salvation. if you have any trouble thinking of this, then this prayer (fraction to the son said at any time) which is from the coptic liturgy may help:http://tasbeha.org/content/community/index.php/topic,13543.0.html
i think there are similar ones in the eastern orthodox churches, but i don't have any links at the moment.
go through your list (written or mental) and sincerely turn away from those sins and ask God's forgiveness.
this may take 15 minutes, or it may take a few hours, depending on you and on God. also, you may have already prayed about most of the list on many other occasions, so it may not take long.
when you come to your time for confession, the priest will pray with you first and this is the time to be calm before God, who is listening with great care and love. then give the priest a chance to talk first and guide the conversation. let him know you have a list, and leave it up to him to decide whether to read it or to let you use it as an aid to memory.
during the confession time, you can ask your confession father for guidance on how to avoid those sins (if you have a repeated temptation, for example).
then after confession, there is a special prayer and the priest tells you God has forgiven you.
this is always beautiful, and it's good to spend the hours following this being calm and grateful (don't go right out afterwards and watch a loud and stimulating movie, for example).
may God guide you (when in doubt, ask God!) and may you have many beautiful years in the church.