I've got some basix tips for ya:
I recommend you just download some good rated tracks here from the exchange so you can see how the advanced coaster builders do this. Just a few basic rules which always go wrong with beginners: Lifthill looks like a banana, always make it out of 3 pieces, begin, straight middle section and the end. You can see this on other peoples coasters. Brakeruns should always be straight just like stations, use right click and select make straight in the menu to make sure they are straight. Also try to prevent the train going to fast in some pieces of the track. You can do this buy just building your track bit by bit. For example, start with station and lift. first drop and loop. Then click connect and go testing. If everything seems fine just go on to the next part of the track for example an overbanked turn and cobra roll. Connect again and make a test ride again. If you notice G spikes (red G's) then go and try to correct them. Smoothing always is hard for beginners. Just do the best you can it is just a matter of getting skill and you'll gain it by just doing the best you can each and every coaster.
I also recommend you download some prefab elements from
http://www.coastercandy.com You can just insert these by click file and select insert element. If right you already have an element pack from Buster which comes with NL. If you notice your ride being to fast in an element during a test run just remove the element again and insert it again but scale it a bit bigger.
Well those were just some tips so your first track will be worth downloading For the really basic things like making turns just look at other people's tracks like i said before [:p]
Greetz GFA