Question: "How can I be filled with the Holy Spirit?"
Answer: An important verse in understanding the filling of the Holy Spirit is John 14:16, where Jesus promised the Spirit would indwell believers and that the indwelling would be permanent. It is important to distinguish the indwelling from the filling of the Spirit. The permanent indwelling of the Spirit is not for a select few believers, but for all believers. There are a number of references in Scripture that support this conclusion. First, the Holy Spirit is a gift given to all believers in Jesus without exception, and no conditions are placed upon this gift except faith in Christ (John 7:37-39). Second, the Holy Spirit is given at the moment of salvation (Ephesians 1:13). Galatians 3:2 emphasizes this same truth, saying that the sealing and indwelling of the Spirit took place at the time of believing. Third, the Holy Spirit indwells believers permanently. The Holy Spirit is given to believers as a down payment, or verification of their future glorification in Christ (2 Corinthians 1:22; Ephesians 4:30).
This is in contrast to the filling of the Spirit referred to in Ephesians 5:18. We should be so completely yielded to the Holy Spirit that He can possess us fully and, in that sense, fill us. Romans 8:9 and Ephesians 1:13-14 states that He dwells within every believer, but He can be grieved (Ephesians 4:30), and His activity within us can be quenched (1 Thessalonians 5:19). When we allow this to happen, we do not experience the fullness of the Spirit's working and His power in and through us. To be filled with the Spirit implies freedom for Him to occupy every part of our lives, guiding and controlling us. Then His power can be exerted through us so that what we do is fruitful to God. The filling of the Spirit does not apply to outward acts alone; it also applies to the innermost thoughts and motives of our actions. Psalm 19:14 says, "May the words of my mouth and the meditation of my heart be pleasing in your sight, O LORD, my Rock and my Redeemer."
Sin is what hinders the filling of the Holy Spirit, and obedience to God is how the filling of the Spirit is maintained. Ephesians 5:18 commands that we be filled with the Spirit; however, it is not praying for the filling of the Holy Spirit that accomplishes the filling. Only our obedience to God's commands allows the Spirit freedom to work within us. Because we are still infected with sin, it is impossible to be filled with the Spirit all of the time. When we sin, we should immediately confess it to God and renew our commitment to being Spirit-filled and Spirit-led.