To harvest the plant you can right-click it. Left-clicking will harvest the plant as well as destroying it. Harvesting Redwheat may yield Redstone Dust and Wheat. Harvesting while destroying may also produce Redwheat Seed Bags.
In order to spawn and grow, Redwheat requires the surrounding light level to be between light levels 5-10. The easiest way to achieve this is using Redstone Torches, which have a light level of 7, though other light sources can be used as long as they are far enough away to lower the light level to within the range Redwheat tolerates. In having a light level slightly brighter than 7, monster spawning can be prevented. Redwheat seed bags cannot be planted if the area is too bright or too dark.
As Redwheat requires a light level between 5-10, it is recommended to cross-breed with crops that grow at night. The reason for this is that crops which require higher light levels will either not cross-breed at all, or will cross-breed very slowly if the light level is just barely within its tolerance range. For best results leave 8 or more empty blocks above the Crops to increase air quality. Light level 8 is ideal, as along with preventing monster spawns, this will eliminate the chance of Hops and Wheat, as well as some other Crops from spawning.
It should be noted that monsters will not spawn on transparent or partial blocks, so if the floor is lined with Micro Blocks, for instance, there will be no reason to pay special mind to light level.
Note: Going by stats, an ideal combination would seem to be Nether Wart and Hops, but when cross-breeding with Hops the light level needs to be kept at 9-10, as Hops needs light to cross-breed. For this reason it is not recommended as Hops and Wheat, which look identical to Redwheat for most of its growth stages, will still spawn.
Redwheat is similar to a Redstone Torch in that it gives out a Redstone signal. Fully grown Redwheat also generates a light level of 7.
A good way to increase the amount of Redstone and Wheat it drops, how fast it grows and how resistant to trampling it is, is to cross breed Redwheat with Redwheat as this has the highest chance of getting a Redwheat. Collect the seed bags, scan them through a Cropnalyzer and then cross breed the two Redwheat seed bags that have the highest statistics with each other as this will often yield even higher stats. Then you can continuously breed the plants with higher stats together until you are satisfied. A more in-depth view of crop stats can be found on the Cross Breeding and GGR pages. The stats are referred to as Growth, Gain and Resistance.