1) Prayer, 2) Preaching of the Word, and 3) Sacraments*:
"[Communion with] all those who, in every place, call upon the name of the Lord Jesus."
[They devoted themselves to the apostles' preaching and to fellowship, to communion, and to prayer] - Acts 2:42
[Because we receive a kingdom^ which cannot be moved, let us have grace, whereby we may serve God acceptably with reverence and godly fear] - Hebrews 12:28

* WCF CHAPTER 26 Of the Communion of Saints
All saints, that are united to Jesus Christ their Head, by his Spirit, and by faith, have fellowship with him in his graces, sufferings, death, resurrection, and glory: and, being united to one another in love, they have communion in each other's gifts and graces, and are obliged to the performance of such duties, public and private, as do conduce to their mutual good, both in the inward and outward man.
2. Saints by profession are bound to maintain an holy fellowship and communion in the worship of God, and in performing such other spiritual services as tend to their mutual edification; as also in relieving each other in outward things, according to their several abilities and necessities. Which communion, as God offers opportunity, is to be extended unto all those who, in every place, call upon the name of the Lord Jesus.

* WCF CHAPTER 29 Of the Lord's Supper
Our Lord Jesus, in the night wherein he was betrayed, instituted the sacrament of his body and blood, called the Lord's Supper, to be observed in his church, unto the end of the world, for the perpetual remembrance of the sacrifice of himself in his death; the sealing all benefits thereof unto true believers, their spiritual nourishment and growth in him, their further engagement in and to all duties which they owe unto him; and, to be a bond and pledge of their communion with him, and with each other, as members of his mystical body.

A note about Saving and Sanctifying Grace from http://www.shortercatechism.com/resources/beattie/wsc_be_088-090.html:
It is worthy of further remark that the term means has a well-defined signification. As means of grace the word, the sacraments, and prayer, are mere channels through which grace is conveyed by divine appointment. In no proper sense are they agents, or are they possessed of inherent efficiency in themselves. The real agent in sanctification is the Holy Spirit. He it is who uses the word, or the sacraments to the spiritual benefit and growth in grace of believers, but these ordinances are in themselves ineffectual to this end. And on the believer's part the exercise of faith, which itself is due to the Spirit's work, is the condition of the spiritual efficacy of these means. There is no inherent virtue in any of these means, as will be seen more fully later on. The Spirit's work and the office of faith are needed.

The Catechisms present these means of grace from still another point of view. The question is raised as to the things which God requires of men that they may escape his wrath and curse due to them for their sins. The answer is threefold. They must have faith in Christ, repentance toward God, and a diligent use of the outward and ordinary means whereby Christ gives to them the benefits of his mediation. From this point of view they are means of salvation, in the full sense of the term. But, without further delay, the general exposition of the word as a means of grace must be entered on.

^ To see more about the connection between grace and the Kingdom, please see www.covenant.net/SpheresKingdomManifesto