While it is often said that the website is the front door of a church today, there is also the real possibility your church's sign can draw in or repel guests.
While there is nothing that makes a church better off spiritually about a sign along the street or on a building, it can repel passerby's and make them resent a church. Over several years this can bring about less first time guests and then create negative talk about your church in the community.
What do you need to look for putting together a great church sign?
1. Make the logo small. You might think your logo is really great, but most people do not care. The real purpose of a sign is to convey to someone who doesn't know all about your logo what is really there. It should say "so and so church."
2. Do not try to put every detail on a sign. The more words, the smaller they all must be, and then the less you can make the main point, which is to identify what church it is. The classic example of this is a small sign below the name with tiny font of every Bible study and service hour. This is hard to read, and has been replaced by website info today.
3. Sharp looking and up to date. Nothing screams "do not visit here" like an outdated sign. Something that is stuck in the 1970's (one church I saw actually had a Koa camp looking sign) or 1960's (weird orange brick and rust anyone?) is hurting people visiting your church. An outdated sign reflects a low priority on excellence (which is not biblical, see the woman who pours perfume on Jesus' feet and see the detail going into the several worship Temples of Israel). It also reflects we don't care about anyone but ourselves to guests if it is outdated. It's the wrong message: we don't care if you visit, we're a country club church. And that is the worst message.
4. Power. It is very expensive to run electric today. Close to a usable power source is the way to go. Then you can put more money into the better sign. The exception would be if the sign is so far from foot and car traffic that you just have to run more. Or if the sign uses different power requiring a different line. Either way, having a lit sign or moving LED sign is the way to go. A sign that is just dark at night doesn't do you any favors.
5. Style. Who are you trying to tell "you belong here!" The fact is a sign says a lot about a church. Is the congregation inside older, younger, in between? An outdated sign implies it is a church of yester year. If you want people who are looking for yester year, then keep that one. But a new sign can be either traditional or contemporary, and this is important: it looks like things are happening today. You'll likely then also be able to use the style of font and sign to give a hint strong enough to get someone's curiosity to visit. Sit down and think through what style you want to convey. Vintage? Classic? Ultra-contemporary?
These are a great start and put you probably ahead of 90% of church signs which are not helping encourage curiosity, but are viewed negatively as eye sores in a community by those driving by.