Bonn

Bonn is a city in the German Bundesland North Rhine-Westphalia.

Bonn was the capital of Germany from 1949 till 1990.

South towards Frankfurt am Main, Stuttgart
To hitchhike direction Frankfurt am Main or Stuttgart, the petrol station on the A3 is a really good spot. Lots of traffic there. From the main station take the line #66 direction Siegburg Bahnhof.
 * short walking connection: Take the bus #509 (only runs 1 time per hour) direction Lange Lindenstrasse. Get off at Bernhardstraße. Walk Alte Poststrasse along uphill, all the way to the petrol station. it's about 5 to 10 minutes walk (for direction North get over the walkbridge).
 * frequent connection: Buses 510, 511, 576 and 577 are going more frequent. Get off at "Schwimmbad". Walk 20 meters back, walk down "Am Stadion" on the right and then "Bernhardstraße" until "Alte Poststrasse".

Another possibility, far easier to reach but less ideal in terms of finding the right lift, is the Shell petrol station on the St. Augustinerstraße. Take the same line #66 as above, but get out at station Adelheidisstraße, the fourth stop after the main station. Walk back 50m on the side of the road heading out of Bonn (there are petrol stations in both directions). There will be lots of local visitors, check out the number plates filtering out those with 'BN' or 'SU' because these are from Bonn and Siegburg, respectively. They might go out in A3 direction, but less probably so than other plates. Ask if people are heading for A3 and if you could be taken to a petrol station there. A station on the A59 will do fine too.

If you are not sure about in which side you should wait, the side on Bonn is to the south. Asking the employees in the gas station where to stand may not be helpful as mostly they don't have any idea and this can cost you time.

South (B9, Remagen, Andernach, Koblenz, Mainz)
From the center walk to the Adenauerallee which leads into the Friedrich-Ebert-Allee, you are already on the B9, you can hitch from every possible spot here, where a car is able to stop. You won't get very long rides, but if you want to go to Koblenz or Mainz, it is the better choice to hitch this national road. Aware, the road is mostly two-laned, so make sure you will get dropped in a save spot (Remagen, or Bad Breisig) where the road is interrupted by traffic lights and where are bus stops where you can hitch on further.

North towards Köln, Oberhausen
In this direction you also need to get on the A3 (see South towards Frankfurt above). You can use both options – the A3 petrol station has stations on both sides which are connected via a pedestrian bridge, and from the station at Augustinerstrasse you can get north and south.

Mind that Köln (Cologne) is part of the same metropolitan area as Bonn and is connected via public transportation. Once on A3, ask for lifts to Oberhausen, because getting to Köln itself is of no use.

Bonn