Starting from scratch can be painful. Luckily there’s a tool out there that can help: PyQGIS Plugin Builder. The form will build a minimal plugin for you. You’ll get a ready QGIS 1.0 plugin that implements an empty dialog with Ok and Close buttons. You can find a step-by-step description on how to create and modify this dummy plugin at linfiniti.com – “A simple QGIS python tutorial”.

From there, I suggest moving to the PyQGIS Cookbook – a great resource for everything related to QGIS with Python – especially the part about “Developing Python Plugins”. Tim also created a PDF version of the Cookbook (original post) if you prefer it in hard copy.

The following code snippet contains the constructor of a GUI control class for QGIS plugins. It’s job is to initialize the plugin GUI (a dock widget in this case) and create signal connections:

import os
from PyQt4.QtCore import *
from PyQt4.QtGui import *
from PyQt4 import uic
from qgis.core import *

class MyGuiControl(QObject):
    """This class controls all plugin-related GUI elements."""

    def __init__ (self,iface):
        """initialize the GUI control"""
        QObject.__init__(self)
        self.iface = iface

        # load the form
        path = os.path.dirname( os.path.abspath( __file__ ) )
        self.dock = uic.loadUi( os.path.join( path, "mywidget.ui" ) )
        self.iface.addDockWidget( Qt.RightDockWidgetArea, self.dock )

        # connect to gui signals
        QObject.connect(self.dock...
        ...

Using uic.loadUi is a convenient way to create a user interface with minimum effort. Of course the performance might be better if we compile the .ui code to python first, but during development phase this saves us an extra step.