I was in New Orleans years ago and was approached by a man asking for money. I took out my wallet and gave him five dollars. He took it, looked at it with disgust and said "that's all?"
We also have local food banks and yes, the cars in the line are very often nicer than mine.
@MossRoad makes a good point that many of those cars might be people picking up stuff for others. I had never thought about that. But most, I fear, are not. Many of the "poor" around here have nice cars, new cell phones, new Nikes etc.
These experience and many like it put me off from giving to beggars. (For the record, it never put me off giving to organized and trusted charities.)
Years later I was reading the Sermon On the Mount. It said, simply, "Give to everyone who asks of you." There were no qualifications, no exceptions. After that, if people ask I try to give if I have it. And that can be hard. Sometimes I am pretty sure that money is going to buy drugs or alcohol. I try to keep the bitterness in check though as it does me more harm than good. And who knows, an act of kindness may be more meaningful and helpful to someone than the material gift that was given.
I'm not perfect and so if I'm certain that I am being scammed I will not give. In our area there are organized groups of beggars who essentially have a 'pimp' who drives them around to different parts of town and gets a large cut of what they take in. The local police have asked the local public not to give because it makes the problem worse and the person you give to isn't going to keep much of it.
But in the end, if we let the people who abuse charity end charity then those in need are the ones who suffer.
Finally, we give regularly to a local food bank that vets the families and people they give to. They have to qualify. It takes a lot of organization and a larger staff to do so of course. I know that isn't realistic for many donor groups so I'm not saying that's the way it 'should' be done but it is another way to do it. This particular charity is also very transparent with its budget and funding and their overhead is very low.