When it comes to bringing the Gospel to a person and making disciples, there are four kinds of people you can be:
You can be the one who prepares the ground: removing rocks from the soil, turning over the dirt, and generally getting the ground ready to plant.
You can be the one who plants the seed: dropping a kernel of the Gospel into (hopefully) prepared soil.
You can be the one who weeds and waters: nurturing the seed as it grows into a fully-formed plant.
You can be the one who harvests: collecting the final result.
Of course, it's exciting to be in the category of harvester. But the reality is, any one of us can find ourselves pretty randomly in any one of the categories when we are around someone else, and it's often difficult to know which category we're in. Should we be preparing the ground? Pouring water on? planting seed? What to do?
"Random acts of kindness" are well and good in terms of preparing ground and watering seeds. Sharing the gospel randomly with strangers can plant seeds. We should all be prepared to "sow a word in season" wherever we are. I've tried to do this myself in a variety of settings, but you never really know what the results were.
The alternative is to build long-term relationships with people, and get to know them so you know what "category" they're in at any given moment. One of Beyond's field leaders has often shared about going for a walk around his neighborhood each day, and knowing--through ongoing conversations--where each of his neighbors are in their spiritual journey. Each day's conversation might be just "one step forward" in that spiritual journey, but by being in someone's life over a longer period of time, we have more of a chance to make an impact.
Here's a simple way to implement this: start a conversation with someone in your life, in your neighborhood, at your work. When they share a problem, consider asking something like: "Ouch. How can I pray for you about that?" As the Spirit leads, either pray for them right there and then, or else pray later. Then--and here's the key--follow-up at an appropriate time - "Hey, I prayed for you. How's that going?"
These kinds of conversations, in non-threatening ways, can have an enormous impact over time.