Just ask.
Are you afraid of making mistakes? Maybe, just maybe, that's a sign that you desire to please God above yourself. A good sign. It takes a special work of God's grace and love in our hearts to be brought to a place where all we can do is walk on pins and needles, not wanting to offend God in the slightest. Because if we didn't care at all about our sins and foibles (perceived and non), how would God feel? Hint: He cares more about our obedience than do we. And He's here to help us.
Oh, one more thing before we begin: worrying about it is displeasing to God as well.
David prays in Psalm nineteen: "cleanse Thou me from secret faults. Keep back Thy servant also from presumptuous sins; let them not have dominion over me:" (verses 12, 13) David didn't even know what he was capable of when it came to offending God, so he offers up this request so that God knows he may or may not be aware of the times that he offended God with something less than love and holiness. Well, God already knows, but at least He and David are now on the same page. That word "presumptuous" essentially means "arrogant". Or blind, maybe? If you think about it, the arrogance that you encounter in yourself and others is essentially caused by blindness. Anytime I think that I know it all, I'm blind. The psalmist prays in Psalm 119: (verse 18) "Open Thou mine eyes, that I may behold wondrous things out of Thy law." We truly need the probing perspicacity of God to enable us to walk before Him and not sideline Him through blind offense. A system of checks and balances, as it were.
Just ask.
David prays again in Psalm 141 (verse 3): "Set a watch, O Lord, before my mouth; keep the door of my lips." Moving forward, James is quite incisive when he says "the tongue can no man tame; it is an unruly evil, full of deadly poison." (James 3:8). When Jesus says (Matthew 12:36) that "every idle word that [we] shall speak, [we] shall give account thereof in the day of judgment", I want to make sure that my words are chosen carefully and wisely. It takes practice and lots of grace, but it's definitely a worthwhile endeavor. Paul, in speaking to the Ephesians (4:29), says to "Let no corrupt communication proceed out of your mouth, but that which is good to the use of edifying, that it may minister grace to the hearers." From these four references, we get a pretty good picture of God's desire that our conversation (literally and figuratively) be colored by that which is pleasing to Him. Make a practice of thinking before you speak. "Be swift to hear, slow to speak..." (James 1:19) and when you do say something, "let your speech be alway with grace, seasoned with salt..." (Colossians 4:6).
What can we do to get closer to the Holy Spirit so that we know when we're about to offend Him? This is a serious question, and one that we need to ask ourselves regularly. Honestly, I have ideas for my own life, but each of us has a relationship with Him that is not defined by what anyone else says, except for the Word of God. So going back to what I said about walking on pins and needles, take heart! The fact that you even care and you want to polish your walk so that it shines, is proof positive that God has brought you closer to Him than you had previously known. My, how dull I can be. "So foolish was I, and ignorant" says Asaph in Psalm 73 (verse 22). It's as if God has to show me, both when I'm in pride and when I'm obedient.
Another good sign, is the overarching realization that we care more about God, Himself, than any of this stuff. Because He certainly cares more about us than this stuff. Notice what David says in Psalm 37:23, "The steps of a good man (and woman) are ordered by the Lord: and He delighteth in [their] way." God is the one who is pleased when we obey. This might sound obvious, but think about it from His perspective. We're His children. He bought us with His blood and He's paying the bills. It looks bad on Him (so to speak) when we're not living in His love, and walking in His grace. I believe that the more we acknowledge God "in all [our] ways" (Proverbs 3:6), the more we'll be sensitive to the slightest slip-up. This is how holiness is achieved, ladies and gentlemen. It's not impossible, it's just a process. Think about it.
"I will instruct thee and teach thee in the way which thou shalt go: I will guide thee with mine eye." (Psalm 32:8) He'll check. Then He'll keep us balanced.
Just ask.