Look on the inside of your tank. You will find a water level index line either painted on or embossed in the porcelan on the inside of the tank wall.

Make sure the water level in the tank is up to the water level index line. If not, adjust the float on the fill valve.

Next, you will see a small tube from the fill valve that is connected to the top of the standpipe. Make sure that line is installed correctly so that all the water discharging from the line goes down the standpipe.

Sometimes new tank flush valves will have a bottom projection that is so long as to partially block the flow of water from the tank into the bowl. This will make flushing sluggish. The water from the tank needs to flow into the bowl quickly. To test bowl function, pour a bucket of water into the bowl. If it flushes well, the problem is with the tank. If not, the problem is with the bowl or the drain.

Thanks lazypup and bus driver,
I'll try a few of the the things you mentioned and see if that helps. I'll probably be back with more questions.
Thanks!