The most important thing to do during discernment is to pray. Ask the Lord to show you the plan he has for your life.
Spend time with Jesus in the Blessed Sacrament during adoration and be open to the promptings of the Holy Spirit. Adopt a daily rosary practice and ask Mary to help you surrender to God's will and have the courage to follow it, just as she did.
Attend Mass as often as possible, preferably daily. As you receive communion ask Jesus to show you your vocation. Go to Confession regularly and read Sacred Scripture and other spiritual books such as the lives of the saints.
Seek counsel from your parish priest, a deacon or consecrated religious or someone trained in spiritual direction. Find a retreat or visit a seminary or religious order during a discernment weekend.