What kind of lighting system are you asking about? Is it outdoor/landscape lighting?

The voltage at an LV fixture is highly dependent on the distance from the remote transformer.

This question probably belongs in the electrical wiring forum.

Follow the specifications on the transformer. Some have multiple taps for more than one lead, others allow two leads from a single tap, but it must be wired properly. It all depends, but there are choices for you; a legit dealer will guide you through the process.
Casey

Low voltage outdoor lighting (i.e. landscape lighting) transformers are supposed to be mounted outside due to UL listing codes. If a transformer is approved for outdoor use it actually is supposed to be mounted outside (and not inside). However, off the record, many people do mont them inside (like in a garage or cabana).

The reason for not connecting the first fixture with-in 10' of the transformer is because the lowest output on any low voltage transformer is 12 volts (multitap transformers go from 12v-22v). There is slight variations on actual output (due to some houses may actually have 125v, some 114 v, etc) and accordingly a close fixture may actually be slightly overvolted. If the real output is 12.4 volts, the first fixture will be overvolted. However after 10' voltage drop will make sure that the first fixture is under 12v as a safe guard. You can always mount a fixture closer than 10'--just use 10' of cable and bury the slack.
We manufacture professional grade landscape light fixtures and outdoor lighting transformers and have robust learning areas on our site if you want to learn more.

Here is a link that might be useful: Outdoor lighting transformer