It's no secret that the average Catholic does not practice the faith. For whatever reason, at this point in history there are huge numbers of Catholics who fall into the category of 'baptized but un-catechized.' After each moment of sacramental initiation, whether it be Baptism, Holy Communion, or Confirmation, many are lost to the praying assembly.
Occasionally it happens, though, that someone who has not practiced or considered the faith since their first Holy Communion or Confirmation is led back by circumstances or just ordinary grace. They range from the cautious but curious to the overwhelming zealous and energetic. Whatever their condition, they need a plan. So, having given this 'how get going again in the faith' advice several times in confession or in the parlor, I thought I would post it.
(N.B. This plan is for Catholics who have previously begun their sacramental initation as infants or children, and are coming back to the faith. The situation of catechumens--those who are adult candidates for Baptism--and baptized Christians of other Churches and ecclesial communities is a different case.)
Attend Sunday Mass as devoutly as you can. Get yourself a Sunday Missal or Daily Roman Missal to help you prepare ahead of time as well as become more familiar with the Mass in general. A good hand missal will also have a lot of other good resources for your prayerful exploration.
Develop a practice of going to confession to receive the Sacrament of Reconciliation. Once every couple of months, with extra effort for Advent and Lent is a good minimum schedule for a devout soul. If you don't have anything to say, either you have a bad memory or your sin is that you aren't reflecting on your life. If you are struggling with serious and habitual sins, go more often.
Pray each day. It doesn't matter how, though a mixture of formal prayers and simple quiet before the Lord is good. Find the time of day when you can pray with the least distraction. For many people this is the peace of the early morning before things get crazy. For others it's the evening after the day has been dealt with. For some with a bi-phasic workday (like a parish priest) the afternoon might be the best time for prayer. Try different forms and practices of prayer and follow what catches your heart. If you don't have a rosary, get one. If you have one on your car mirror, take it down and pray it instead.
If you are not an active member of your parish, become one. In most cases you are a parishioner of the parish territory in which you live, which is usually the closest Catholic church. However, you can also make yourself a parishioner of a parish somewhere else simply by registering there. Go where you feel your soul will be fed. Support your parish with your prayer, your good example, and a weekly financial contribution.
If you don't have your own copy of the Sacred Scriptures, get one. The standard American English Bible for Catholics is called the New American Bible.
Empower yourself by learning the faith and the teachings of the Church. Pick up a catechism. For those in the States, the Catholic Catechism for Adults by our bishops is very good, and is usually in stock in regular bookstores. If you want to go first class, the Catechism of the Catholic Church is a great reference, and is available everywhere. When one person (even a priest!) says that the Church teaches this or that, and someone else says the teaching is something else, you don't have to wonder. Learn it yourself.
Visit a Catholic bookstore when you can, and browse the spiritual books. If something grabs your attention, pick it up.
Discern and adjust your life
Through prayer and learning you will soon notice ways in which you need to bring your life more in line with Catholic teaching.
If you have not completed your sacramental initiation, begin this process right away. In many cases this means that Confirmation is still lacking. Most parishes will have a program for this, or can direct you to one.
If you are struggling with serious, habitual sin, find a confessor whom you feel takes you seriously and can offer practical advice. Do a little detective work on yourself. Ask what this sin does for you. When does it happen? What are the occasions of the sin? What is the opposite virtue and what are the practical means of acquiring it?
There are many lifestyle and marriage situations which may need adjustment. Some marriages outside the Church are easily regularized according to Catholic practice, while others may be more complicated. Talk to a priest whom you trust, and then pray to the Holy Spirit to show you opportunities to speak and pray with your spouse about it. The same goes for those who are not married, but may be simulating marriage through cohabitation. Ask the Holy Spirit to help you notice opportunities to open the subject of the Church's expectations of the two of you.
Take it easy! The plan for this life is to walk with the Lord, so there's no need to run. This is a work of grace; it's not your own. Your job is not to push, but to consent. Attend to the graces at hand, stay grateful, and take it one day at a time.