Hopefully this warning is unnecessary. Be very careful when observing Venus during the day as it is often quite close to the sun and you could blind yourself if you accidently get the sun in your scope.
The easiest way is with a goto telescope. Set it for Jupiter or Venus or whatever and away it goes. Use a low power eyepiece and get it centred and then go to higher power.
If you don't have a goto, then it's a bit more difficult...
Use some sky software and figure out where the object is. Best way is to determine the azimuth and altitude. Then with a compass and something to measure the angle, figure out where it is. Then use binoculars to find the object. Its a good idea to have some sort of reference - like put a deck-chair in a location so that a roof or some object is in the field of view to give you a reference and then sweep the sky with the binocs. Once you've found the object and can reference it to the roof or whatever, then point your 'scope.
I've had a look at Mercury, Venus, Mars, Jupiter and Saturn during the day. Also Sirius, Canopus, A Centauri, B Centauri, Vega, Beetlejuice and a dozen or so other stars as well as a few comets. I've found all these with my ED80 or a 150 mm Mak.
There is not a huge amount to see - the contrast is really washed out, although some different coloured filters may help.
Obviously, you need to take care not to fry your eyeballs or other parts of yourself or equipment. With something like Mercury and Venus in particular, a great deal of care is needed. You may need to extend the tube or make some sort of sunshade to block the sunlight as even some sun coming down the tube but not even going on the mirror or lens may give enough reflection of the inside of the tube to fry you.
You don't really need any filters, but if you try different filters - red, orange etc and also polarisers, you may get better contrast between the blue sky and the objects.
The easiest way to avoid the Sun is to set it up in the shade and ensure that none of the scope catches the Sun. Of course you will need to check this shade as the day progresses so you don't suddenly find yourself out of the shade! When I have done this myself and have had to set up in the Sun, put the cap over the top as you move the scope around to a different target.
