Deciding where to place a landing page contact form, and how long does the form need to be to achieve maximum effect, is part science and part art. We know that contact forms, and forms in general, are an important part of lead generation. Getting people to sign to newsletters, to access content that will help them make decisions, or to ask them for information so they could try your product takes some mixing and matching in order to be done correctly. But if you look at it carefully, you will see that form length and placement in your sales funnel are the two things you need to get right in order to get your target audience to share the information you want them to.
Casting the Widest Net
If you place a contact form at the top of your marketing funnel, you're casting a wide net in order to get as many leads as possible. Top of the funnel contact forms are geared towards attracting anyone who visits the landing page, regardless of the purchasing phase they're in.
To be able to get people with low commitment levels to give you their information, it's important that you provide them a hassle-free experience and not ask for much. You want to use the really short contact forms, the "name + email" forms, and you want to offer them simple things like blog subscriptions or ebooks.
Even though these short forms placed at the top of the funnel are designed to catch as many prospective buyers, you can use the information they provide to you, even if it's only a name and an email address, to cultivate these leads and move them further down the funnel.
Being More Specific
When you place a contact form somewhere in the middle of your marketing funnel, you can get away with asking for a bit more information. By this time, leads should be more committed to making a purchase - in fact, the middle field of the funnel is where people should be in the consideration stage of the buying process, which is a step or two away from making the actual purchase.
At this stage, it would be useful if you provided them with some information that will help them gauge their purchase. Whatever type of content you can provide to them that will help them justify the purchase would be good; content that also suggests that they should make their purchase with your business is that you're aiming for. From case studies to brochures, whatever you can produce will help. When the time comes to ask them for their information, you can get away with adding a field or two to the basic "name + email" form, but don't ask them for too much information yet.
The Purchasing Stage
By the time they get to the end of your marketing funnel, people should be in the purchasing stage - they should know what is it they want to buy, and they only need that little push to get them to buy from you.
At this stage, you'll usually see businesses ask for as much qualifying information as they think they can get away with. The reasoning behind this is simple - the more information you have about a lead, the better you'll be able to tailor any further communication to fit their specific needs. It makes sense to invest the most effort in the customers you know are looking to buy and not just window shopping and those customers are also more likely to go along and provide you with the information you want. Of course, you have to give them something in return, and this is the time where you can whip out your free demos or trial periods.